Micro-resistance spot welding is widely applied to series-parallel connections of power 18650 lithium batteries,but the reliability of welding quality cannot be detected. In this paper,the micro-resistance spot welding quality of the nickel-plated steel sheet and 18650 battery shell is researched. By appropriate thermal excitation and high frame rate infrared thermal imager,the infrared thermal images are collected. The relationship between the thermal image change with time and the nugget is studied to judge the joint quality of 18650 battery micro-resistance spot welding. The results show that the microresistance spot welding joint with different qualities under the same thermal excitation,the faster the temperature of the welding spot position drops,the sooner the clear contour of the welding spot image appears,which means the better the bonding state of the welded joint,that is,the larger the nugget area will be.