The model of the postprocessing system of the direct injection gasoline engine was designed by AVL BOOST software, which is a combination model of Three Way Catalytic and Gasoline engine Particulate Filter（Gasoline particulate filter，GPF）. The effects of the WLTC (Worldwide Lightduty Test Cycle) circulatory conditions on the HC conversion efficiency of the model and the effects of the filter efficiency and pressure drop of the gasoline particulate filter were investigated. The results show that the efficiency of the threeway catalytic converter converting HC is about 90% in the combined model of threeway catalytic converter and gasoline particulate filter under the circumstance of WLTC. The pressure drop of the particulate filter of the gasoline engine under the WLTC cycle condition is greatly affected by the exhaust gas flow rate, and the line graph of the pressure drop of the gasoline engine particulate filter is basically the same as the exhaust gas flow line graph. The particle filter efficiency of GPF can be stabilized at 90%. The average pressure drop of GPF is between 1 000 Pa and 2 000 Pa, and the maximum pressure drop is 5 500 Pa, which meets the pressure drop requirement of GPF.