A three-cylinder, with a bore of 68.5 mm port fuel injection, engine was adopted to study the combustion and emission characteristics of a methanol/gasoline-fueled engine during cold start and warm up. The cylinder pressure analysis indicates that engine combustion is improved with the methanol addition into gasoline. With the increase of the methanol fraction, the flame developing period and the fast burning period are shortened and the indicated mean effective pressures become higher during the first 50 cycles. Meanwhile, a novel quasi-instantaneous measurement system was designed to measure engine emissions during this process. With the increase of the methanol fraction (below 30%), the unburned hydrocarbon and carbon monoxide (CO) are decreased obviously. The measured results show that the hydrocarbon is reduced about 40% at 5 degrees C and 30% at 15 degrees C during the cold-start and warm-up period; CO is reduced nearly 70% when the engine is fueled with M30 (30% methanol in volume), and a higher difference in the exhaust gas temperature of about 140 degrees C is achieved at 200 s after starting than fueled with gasoline.