Abstract: In view of problem of big estimation error of estimation method of state of charge using lithium battery detection chip DS2786, an estimation method of lithium battery for nodes in wireless sensor network was proposed combined with DS2786 chip and Kalman filter algorithm. In the method, equivalent circuit model which can characterize lithium battery was built, and the open circuit voltage and discharge current of lithium battery obtained by the chip DS2786 were taken as input parameters of Kalman filter algorithm to accurately estimate the state of charge. Experimental results show that the method has estimation error of state of charge of lithium battery less than 3%, low computational complexity, and can meet the application requirements of embedded devices.