Most of the existing DC energy meters are used to measure the DC steady-state energy, which has poor adaptability to the change of voltage and current during the charging process, and ignores the power generated by power fluctuation and high-frequency ripple. Therefore, by studying the principle of DC power generation of rectifier load, switch charging equipment and fast dynamic load, combining with the metering algorithm and experiment of electric energy meter, this paper expounds the error influence in the metering process, and puts forward the optimization method of calculation parameters to reduce the metering error in different metering occasions. It can provide reference for improving the accuracy of electric energy measurement in different measurement occasions, provide ideas for the optimization of DC measurement algorithm, and clarify the direction of improvement.