By using of daily temperature from 1951 to 2003 during heating periods in Taiyuan, the variation characteristics of mean temperatures during heating periods and elements about energy consumption (the dates of first and last days of heating periods, heating degree days, etc.) are analyzed. The result indicates that: the temperatures in heating periods increased significantly, having a jump at the end of the 1980’s; the dates of first days delayed year after year, and the dates of last days show an advanced tendency since the 1990s and remarkable interdecadal changes, thus heating periods shortened year by year; heating degree days showed an obvious decreasing tendency. Based on heating indexes, an analysis of energy saving effect is made, which shows that there is high potential in energy saving in Taiyuan and it is necessary to change the traditional heating pattern.