Abstract: The traditional Newton algorithm has heavy calculation burden and low efficiency, its iterations and time will significantly increase when load type is no longer a constant power. In view of these problems, an improved Newton algorithm for power flow was proposed. The algorithm considers load type to constitute ZIP model with constant power load, constant current load and constant impedance load, and uses matrix splitting and relaxation method of matrix inversion to make the algorithm not only has simple and fast computed process, but also can improve algorithm efficiency and weaken influence of load type on iterations and time. The effectiveness of the algorithm was verified by using 33 nodes system to test and compare the iterations and times. Influence of load types on system voltage was analyzed though power flow calculation results, it shows that increase of constant impedance load proportion can improve system node voltage.