In order to study the influence of the positions of KTiOPO 4 (KTP)crystal in the cavity for the output power of green laser，the inquiry experiments of intracavity and extra cavity frequency doubling green light with Laser Diodes(LD)pumped solid－state laser experiment instrument were designed．The relationship of the frequency doubling efficiency of green light，the power density and the spot radius of the fundamental frequency beam were analyzed． When KTP was at different positions of intracavity and extracavity，output powers of 532 nm frequency doubled green light were measured，respectively．In the experiment of extracavity frequency doubling，two experimental schemes were designed，namely，KTP was at different positions of extra cavity which whether or not have lens．By guiding students to calculate corresponding beam radius of 1 064 nm fundamental frequency light with the theory of cavity and gaussian beam，the reason for the difference of 3532 nm frequency doubling output power of KTP crystal at different positions，and the method of improving frequency doubling efficiency through improving laser power density with lens focusing were analyzed．