Remote sensing has become an important means for monitoring urban heat environment. It is still difficult to quantitatively analyze the spatiotemporal change of the urban heat environment only by ground surface temperature or brightness temperature presently. Based on the examination of remote sensing images, three heat environment monitoring indexes are put forward: urban heat island intensity, heat field intensity index, and urban heat proportion index. The MODIS surface temperature products and FY3A/MERSI of two years are used for monitoring and analyzing the Beijing area heat environment. The results show that the three indexes can monitor the intensity and variation of the Beijing heat island effect, and have significance in urban heat island monitoring.