The invention discloses a measurement method of engine EGR rate, comprising the steps of measuring air intake flow of engine by air flow meter; installing temperature and pressure sensors in front of and behind EGR valve respectively whose openness is controlled by control unit of auto engine to measure pressure Pb and temperature Tb at inlet of waste gas of EGR valve and pressure Pa and temperature Pa at outlet of exhaust gas of EGR valve; calculating flow of exhaust gas, etc. The engine EGR rate measurement method greatly reduces measuring error of EGR rate in lower pressure difference between in front of and behind EGR valve.