With deployment of large scale distributed heat pumps, three-phase load flow considering heat pumps impact is a basic tool to analyze distribution network profile. Due to the rapid development of incremental distribution networks with different investment entities, it is very difficult to achieve both centralized power flow calculation and synchronous power flow calculation considering the factors such as data privacy protection and communication delay. Firstly, three-phase load flow with large scale heat pumps is proposed based on implicit node impedance method. Secondly, asynchronous iterated load flow is proposed based on matrix-split scheme. The proposed method is suitable for distribution network distributed load flow. Finally, the proposed method is validated with IEEE 123 test feeder. This work is supported by National Natural Science Foundation of China (No. 51707196) and Science and Technology Project of State Grid Corporation of China “Simulation Analysis of the Influence of the Electric Heating System on the Power Grid under the Thermoelectric Coupling”.