In order to ensure the inverter efficiency measure result of the grid-connected photovoltaic inverter accurate and reliable . According to GB/T 20514-2006 "the photovoltaic system power regulator efficiency measurement program" and CNAS - GL08” Electric field uncertainty assessment guidelines " ,we use the power analyzer to measure the input and output power of the inverter, and analyze its inverter efficiency when it under the state of 50% rated power. The measurement uncertainty of evaluation results meet the demands to the CNCA/CTS, 0004-2009A” Special grid photovoltaic inverter technology conditions”, and has a certain practicality.