This paper studied the effects of the single -and double -parallel entry ramp of expressway on the mainline traffic flow. Microscopic traffic simulation software VISSIM was used to simulate expressway import parts of the two ramps under different traffic demands. The analysis of such data as vehicle speed, delay and traffic flow from mainline traffic flow shows that when v/c of the main line and import flow is less than about 0.7, the single-and double-parallel entry ramp has little influence on the operation state of the mainline traffic flow, with the main line still maintaining high speed. In case of ramp forms, factors including land space, construction cost and other factors should be given more attention to. When v/c of the main line and import flow is more than about 0.7, vehicle speed fluctuations of the main line traffic flow of the single-and double-parallel entry ramp is the opposite of the present situation. So the choice of ramp forms in accordance with traffic demands is very im- portant for improving the expressway operating efficiency; when the traffic flow approaches saturation, the single- and double-parallel entry ramps are not different in terms of the mainline operation state. The speed-flow analy- sis of mainline three-lane traffic flow shows that the mainline traffic flow presents obvious free flow and conges- tion flow regarding double-parallel entry ramp while the mainline traffic flow keeps steady regarding single-par- allel transport ramp.