Abstract: Based on the condition of the maximized laser gain, the laser gain, the optimal optical crystal length and width of quasithreelevel solidstate slab lasers, which variate with pump power,are analyzed and optimized. At the same time we found that the the concentration of doping medium and the width of the slabs satisfied a certain relation under the condition of diodesidepumped mode in lower pump power. The laser gain, the optical length and width of the slabs are optimized and simulated when pump power changes from 0 to 2kW. These results can also be applied to the design for other quasithreelevel solidstate lasers.