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.