Theoretical research on the mode locking characteristics of mode-locked all-solid-state laser with semiconductor saturable absorber mirror has been carried out. According to theoretical model of suppressing Q-switched mode locking and combining with LD-pumped all-solid-state Yb:YAG laser,the reflectivity of SESAM and the critical pump power of suppressing Q-switched mode locking have been studied by numerical simulated calculations under the conditions of different modulation depths,non-saturable losses,saturation fluences,transmittance of the output mirror and other parameters. When the incident pulse fluences on the SESAM are the same,modulation depth,non-saturable loss and saturation fluence have inverse relations with SESAM reflectivity. With the decrease of modulation depth,saturation fluence,transmittance of the output mirror,beam waist and cavity length,the critical pump power also decreases,and suppressing Q-switched mode locking becomes easier. When the crystal length is 1.9 mm,the minimum critical pump power can be obtained.