We　presented　the　first　demonstration　of　a　new　structure　KD*P　crystal　as　electro-optic　switch,　in　which　the　thermal　depolarization　loss　was　intrinsically　reduced.　The　thermally　induced　birefringence　and　depolarization　of　both　cylindrical　and　rectangular　crystalline　structure　were　simulated.　The　higher　pulse　energy　or　average　power　output　was　achieved　in　the　diode　pumped　E-O　Q-switched　laser　using　a　rectangular　KD*P　crystal.　At　the　repetition　rate　of　100　Hz,　the　maximum　average　output　power　was　27.2　W　at　145　A　pump　current,　corresponding　to　the　pulse　energy　was　272　mJ　with　pulse　width　of　65　ns　and　the　beam　quality　of　M-2=20.4.　Comparing　the　highest　average　power　or　corresponding　single　pulse　energy,　the　laser　with　the　rectangular　KD*P　crystal　was　two　times　of　the　laser　with　the　traditional　cylindrical　KD*P　crystal.