Domestic livestock manure production continues increasing to 139,753 ton/d as of 2020. Among them, cattle manure accounts 41.3% showing the largest amount of total livestock manure production. Approximately 94.9% of the generated cattle manure is treated as compost and sprayed on agricultural land, but compost spraying area will be limited due to the continuous decrease in agricultural land. In addition, environmental problems such as excessive nutrient supply of agricultural land, odor, and greenhouse gas emission are serious. Above-mentioned problems can be solved by switching treatment methods to anaerobic digestion, but the cattle manure includes some non-biodegradable substances such as lignin, cellulose, and hemicellulose, resuling in low biodegradation and digestive efficiencies. Therefore, this study aimed to improve the anaerobic digestion efficiency of cattle manure by deriving optimal conditions for pretreatment, anaerobic co-digestion, and stable continuous operation. The central composite inscribed using Minitab''s response surface methodology was introduced to efficiently derive optimal pretreatment conditions. To select optimal conditions for thermal hydrolysis, microwave, and ultrasound pretreatments, BMP(Biochemical Methane Potential) test were applied with factor conditions derived by Mititab''s central composite inscribed, and then the results were compared. The optimal conditions for thermal hydrolysis pretreatment was deriven under 145.5 ℃ and 45 minutes showing biodegradability of 40.2%. Optimal conditions for the microwave and ultrasound pretreatments were deriven from the conditions of 818 W, 7.4 minutes and 471 W, 41.6 minutes, resulting in 38.9% and 39.2% of methane conversion efficiency, respectively. Methane conversion efficiency were improved when optimal conditions of each method were applied. Methane conversion efficiency were respectively 32%, 28%, and 29% higher in thermal hydrolysis, microwave, and ultrasound pretreatments than that in control. It is well known that the anaerobic digestion of cattle manure is not efficient due to its low C/N ratio and low biodegradability. To solve this problem, food waste(FW) and pig manure(PM) were mixed for anaerobic co-digestion, and the simplex lattice design was introduced to confirm optimal mixing ratio. As a result, anaerobic co-digestion of co-substrate combined with mixture ratio of 30.5:42.5:27.0 (CM:FM:PM) showed the highest performance. The synergy index analysis results showed that the synergistic effect was reinforced as the compositions of cattle and pig manures in co-substrate were increased. Continuous experiment for anaerobic digestion of optimally pretreated and mixed co-substrate was tested under OLR(Orgarnic loading rate) fluctuation condition. For the continuous tests, TCM(Treatment Cattle Manure)+FW+PM reactor was operated with co-substrate mixed at optimal mixture ratio (30.5:42.5:27.0). CM and TCM reactors were operated with single substrate of pretreated and non-pretreated cattle manures, respectively. All continuous reactors were operated under different OLR of which ranges were gradually changed from 1 kg-VS/m3·d (T1) to 7 kg-VS/m3·d (T4). As a result, the organic matter removal rate in CM reactor was decreased during the stage T2, and then pH drop and VFAs(Total Volatile Fatty Acids) accumulation in CM reactor were occurred when the OLR was further increased during the stage T3. For the TCM reactor, although the efficient organic matter removal was maintained during the stage T2, it could not avoid the pH drop and VFAs accumulation at stage T3. In contrast, the TCM+FW+PM reactor maintained efficient performances even OLR increased to 5 kg-VS/m3·d (stage T3), showing stable methane yield and organic matter removal efficiency. However, TCM+FW+PM could not overcome inhibition of pH drop and VFAs accumulation at the stage T4 of which OLR further increased showing drastic decrease in biogas production.