Electron Microprobe Chemical dating (Chemical Th- U- total Pb Isochron Method ，CHIME) has been successfully used on monazite, allanite, zircon, xenotime, uraninite and other accessory minerals. A rare study focused on thorite dating by Electron Microprobe. This paper attempts to use Electron Microprobe to date thorite in Proterozoic pegmatite dikes in the Xiaoqinling gold district, China. In this study we dated minute thorite grains (＜30 μm in size) by electron microprobe analysis. A geologically significant chemical Th- U- total Pb age mean value of 120.9±2.1 Ma (95% confidence interval) was determined. This age is in agreement with the mineralization age of the Qiangma gold deposit and reflects a hydrothermal overprint in the course of lithospheric thinning of the North China Craton, following widespread granite intrusion.