Fair and equitable measurement accuracy of watt-hour meter，the normal distribution model is used to optimize the calibration process of electricity meters, in the traditional calibration process, the confidence judgment of normal distribution , and using the interval distribution principle to increase the phase compensation table algorithm , the measurement requirements of combined error in R46 standard are solved. Studies the optimization and accurate measurement of normal distribution, improves the measurement accuracy of the electricity meter, realize the electricity meter products to meet the international standards, this method has practical application value.