Intake camshaft equipped with continuously adjustable cam phasing units is applied to a 486Q gasoline engine. Phasing strategies are researched through engine cycle simulation to achieve superior engine performance. The simulation results show that at high load and low and moderate speed of the engine，phasing adjustment can lead to 6% to 8% increase in power performance because phasing advance contributes to suppressing intake backflow at IVC(intake valve closed). Cam phases obtained from numerical optimization have good agreement with engine test. At moderate load，cycle simulations show that phasing advance can increase residual gas coefficient from 9% to 20%，and reduce NO emission by 80%，BSFC(brake specific fuel consumption) by 2% at a demonstration operation. With regard to fuel economy and emissions，adjustment and optimization of intake phasing at moderate load are further verified by engine test. At low load，technical approaches to enhance combustion stability，reduce HC emission and improve cold start are investigated. The effectiveness of suppressing exhaust backflow into intake duct by phasing retard is testified by simulation. Phasing changes at the operating condition are optimally obtained by engine test for improvement of combustion stability.