Abstract:Based on consecutive measurement from 1981-1990 at Xiaoliang ExperimentalStation in Guangdong, the energy balance in three ecosystems, mixed forest, eucalyptus forest and bare land, was studied comparatively. The reflection rate to solar radiation wasin the order bare land ＞eucalyptus forest ＞ mixed forest. The net radiation (NR) on bareland was 1.57 times of that on mixed forest and eucalyptus forest. The energy dissipationby evapotranspiration was 95% of NR for mixed forest, 59% of NR for eucalyptus forest and 70％ of NR for bare land．The heat conductivity of soi1 changed a little in different ecosystems and various seasons， but the regularity was not apparent．Annual heat flow through soil was nearly balanced for bare land，which differed from that for mixed forest and eucalyptus forest．As a whole，the heat environment was best in mixed forest and worst in eucalyptus forest，which was shown by that the output of energy from the mixed forest was mainly through evapotranspiration and that from the eucalyptus forest was mainly through air movement．This is why the micro-climate in mixed forest is warm and wet but that in eucalyptus forest is hot and dry．