In this paper, SCR system which is one of de-NOx systems was studied in order to satisfy NOx regulations currently being enhanced. SCR system simulator was fabricated and tested through understanding the characteristics of each component. The experimental parameters were as follows. Flow condition was eleven parameters from 1,500 to 2,500rpm each 100rpm and temperature condition was five parameters from 200 to 400℃ each 50℃ and distance parameter was 4 variable form 10cm to 40cm each 10cm. For the accuracy of the experiment, data were collected about 5 times and the average value of the results was used. As a result of analysis according to engine speed, influence on the mixer in SCR system is grown at higher number of revolutions. and the uniformity was also found to increase slightly. As a result of analysis according to temperature, atomization of the sprayed material became active according to increase temperature and the homogeneity distribution of the catalyst shear was found to increase. The maximum minimum uniformity difference for temperature was found to be around ± 5%. As the distance between the mixer and the catalyst increases, the uniformity tended to increase. and the difference in uniformity between 10cm and 40cm was 8%, indicating that the variable depending on the distance had a large influence on the uniformity. As a result of uniformity according to mixer type, K company''s mixer showed high uniformity in general, and in case of D company, two types of mixing shapes were observed. In the case of the mixing shape A, spraying and uniformity were locally distributed than the uniformity tended to be lowered. In the case of Mixing Shape B, spraying and uniformity were standardized as a whole than uniformity index was increased. As a result of comparison between mixers of K company and D company, efficiency of over 90% was achieved at approximately 30cm for K company’s mixer and average uniformity for D company’s mixer was 90% uniformity over 40cm area except low rpm. Overall, the influence of SCR reductant on the uniformity distribution was analyzed according to rpm, temperature, distance, mixer shape. Base on this paper, that will contribute to the technical part in SCR system component development was expected.