Considering the anthropogenic heat (AH) flux sources from human metabolism and activity, factories, vehicular traffic, this work has estimated the diurnal and annual variations of AH flux in Guangzhou from 2000 to 2011 using 2001-2012 data obtained from the Statistics Annals of Guangzhou. The results show that the averaged AH flux of factories and vehicular traffic accounts for 55% and 36%, respectively. The AH flux value shows an increasing trend during the 12-year period from 2.7×1017 J to 4.4×1017 J, with an exception after 2006 when the value presents a slight decline. This result can be attributed to a higher energy efficiency leading to a lower emission rate of energy consumption as manufactories are the major source of AH flux. The peak values of diurnal variation is shown to occur at 1000 LST and 1400 LST. During the 12-year period, the overall diurnal variation shows a decreased trend, which can be attributed mainly to a faster pace of urbanization than the increasing rate of energy consumption, population, and vehicles. Compared with the diurnal variation parameters of AH flux in the urban module of the Weather Research and Forecasting (WRF) model, this discrepancy is closely related to discrepancies in work and life span between Guangzhou and cities in western countries.