Abstract: Mo thin films are the preferred material for the back electrode of CIGS solar cells, which puts forward great demands on the adhesion strength between the thin films and the substrate. To improve the adhesion strength, the effect of three factors (depositing temperature, vacuum degree, and sputtering power) on adhesion strength with the help of L₉(3³) orthogonal table was studied and three levels were selected for each factor. The indentation method was used to measure the adhesion strength between films and substrates. The evaluation criterion of the adhesion strength was the area of indentation-induced cracks, which could be obtained by the improved Uddeholm method. Through range analysis, the R values of depositing temperature, vacuum degree, and sputtering power were 6.51, 18.29, and 5.96, respectively. The optimal combination was A₁B₂C₃, and the area of cracks was the smallest at that time, which was 2.41. Results show that the effect of vacuum degree on adhesion strength is the largest, then depositing temperature, while the effect of sputtering power is the least. Considering the three factors, the optimal sputtering parameter combination is: power 150 W, pressure 0.5 Pa, and temperature 100 ℃.