In view of the problem that the APF (active power filter) control system is not high real-time for data acquisition and the amount of transmission data is limited,designing the real-time data acquisition and monitoring system for APF based on LWIP.This paper introduces the timing control of data transmission between upper and lower computer in detail,including the software functions for data organization and transmission of DSP, data receiving and dispatching of ARM, data receiving and transmission of the upper computer and so on.At the same time, the system also introduces the function of setting new control parameters by the host computer when APF is running.Through experiments,the feasibility and effectiveness of the system control parameters transmission and 15 real-time data updating under 32K sampling frequency were verified.