Thermal　depolarization　caused　by　birefringence　is　a　major　factor　that　limits　the　output　power　of　linearly　polarized　Nd:YAG　laser.　This　paper　theoretically　analyzes　the　thermal　depolarization　of　[111]-　and　[100]-cut　Nd:YAG　rods　and　output　power　of　two　diode-pumped　Nd:YAG　rods　are　compared　experimentally.　φ3×80　mm　sized　[111]-　and　[100]-　cut　rods　with　doping　concentration　of　1.1±0.1at.%　are　used.　With　a　pump　power　of　180　W,　the　ratio　of　linearly　polarized　output　power　versus　unpolarized　output　power　obtained　with　the　[111]-　and　[100]-　cut　rods　are　19%　and　43%　respectively,　with　a　difference　of　24%.　The　experiment　demonstrates　that　in　comparison　with　conventional　[111]-　cut　Nd:YAG　rod,　[100]-　cut　Nd:YAG　rod　can　improve　the　linearly　polarized　output　power　obviously.　The　thermal　depolarization　depends　on　the　polarization　direction　for　the　[100]-　cut　Nd:YAG　rod,　and　the　linearly　polarized　output　power　can　be　improved　by　suitably　modification　of　the　polarization　direction　of　linearly　polarized　laser　to　minimize　thermal　depolarization.　©　2012　Chinese　Optics　Letter.