Many　building　simulation　software,　such　as　Hongye,　DeST,　Energyplus　and　so　on,　are　widely　used　in　determining　cooling　loads　of　buildings　in　China.　The　problem　is　that　the　simulated　cooling　loads　for　the　same　building　differs　each　other　greatly　for　different　software.　Taking　Hongye　and　DeST　as　examples,　this　paper　tries　to　find　what　cause　the　deviations　of　simulation　results　in　thermal　modeling　of　the　two　software.　Simulations　of　cooling　loads　have　been　carried　out　for　a　specified　building　using　the　two　softwares　separately,　and　simulation　results　have　been　compared.　Some　parameters　are　adjusted　to　see　to　what　extent　the　deviations　of　simulated　cooling　loads　between　Hongye　and　DeST　have　been　decreased.　Results　show　that　the　deviations　of　simulation　results　are　mainly　due　to　the　difference　of　the　calculation　method　of　long-wave　radiation　heat　exchange　and　the　difference　in　the　way　simulating　thermal　effect　of　solar　radiations　through　glass　windows　for　the　two　softwares.