Generally, excavator is used to work on unpaved road. When excavator is used to work on unpaved road, usually only three or four rollers endure the whole weight of excavator. Also excavator will be impacted by external shock a lot because of the heavy and hard objects like stones on unpaved road. It is necessary to have a method to measure the loads on rollers and predict the working life of them. Therefore, it is necessary to develop an excavator model for dynamic analysis. Excavator can be divided into two major parts: upper part and lower part. This thesis is focused on the lower part of excavator. Comparing the experimental results and analysis results, the thesis will verify whether the dynamic analysis method can be used for excavator model or not.