The effect of percentage depth dose (PDD) and total scatter factor should be inspected in clinical prescription dose calculation. In this study, the simulation of SIEMENS Primus Plus accelerator and calculation of the total scatter calibrate factor (,S,c,p,) and percentage depth dose (PDD) of 6MV electron beam energy was made by use of Monte-Carlo method (BEAMnrc and DOSXYZnrc). And the results were compared with the measured one by use of thimble chamber. What’s more, the effect of radiation field and depth on total scatter calibrate factor (,S,c,p,) of linear accelerator was also calculated in Monte-Carlo method. The results show that the total scatter calibrate factor (,S,c,p,) increases with increment of field size and the scatter calibrate factor (,S,c,p,) increases with the increment of depth when field size is larger than 10 cm×10 cm. However, the total scatter calibrate factor (,S,c,p,) decreases with the increment of depth when field size was smaller than 10 cm×10 cm. It has been confirmed that Monte-Carlo method can establish a comprehensive and accurate information on the scatter calibrate factor for clinical radiotherapy, which may provide more realizable quality assurance and control.