The vehicle emission test of heavy vehicle is one of the important test items of China Ⅵ emission regulation. Taking China Ⅵ heavyduty natural gas engine as the research object, the engine bench WHTC cycle and the PEMS real world emission test were respectively carried out, and the engine operating conditions and emission test results were compared and analyzed. The results show that engine operating conditions of the two methods are similar to some extent, but engine exhaust temperature of WHTC has a quick rise and the excess air coefficient has a little fluctuation so that threeway catalytic converter has high catalytic conversion efficiency. The pollutant emission of both methods can meet the limit requirements of China Ⅵ emission,  but a certain difference between them exists due to the change of engine operating conditions and external conditions. The bench WHTC cycle emission is lower and the differences of NO_x, CO and THC specific emission are 16.41%, 20.2% and 15.8% respectively. Accordingly, the development and calibration of engine needs to take into account the two operating conditions to leave more allowance for emissions.