Abstract: The measurement data fluctuates greatly when the distribution network is not powered off, and the test accuracy of the common electric energy itemized measurement error test method is not high. Based on this,the electric energy itemized measurement error test method under the condition of distribution network not powered off is proposed. This paper first designs the measurement data input and merging unit,adds the signal conditioning circuit on the basis of the original merging unit,redefines the effective digits of the A/D converter,obtains the real measurement data, deduces the sub item measurement quantization error of electric energy based on the measurement data, obtains the test target, and then uses Multisim software to build the measurement error signal simulation model,Process the error data and error signal.Finally,input the processed data into the analysis unit,carry out harmonic transformation under the condition of uninterrupted power supply of distribution network, and complete the error test of electric energy sub metering. The experimental results show that the minimum relative uncertainty of voltage finite value square is 0.03 and the minimum relative uncertainty of active power is 0.48. Its quantization error does not affect the measurement accuracy;The test error of this method is only 0.2%,with high test accuracy and reliable signal. It has great application value and is worth popularizing.