To clear the best limiting speed strategy in urban expressway ramp merging area, based on the principle of limiting speed on ramp merging area, the effects of speed distribution, relationship between volume and speed, speed distribution in various lane position, vehicle type and lane width on the appropriate speed of ramp vehicles were studied by actual measured data of expressway and mathematical statistics. The result shows that the speed from inside to outside is decreased, and mainly affected by the traffic flow. Traffic speed characteristics are different between ramp merging area and basic road section, and different speed limit strategy should be formulated, the value should be determined according to the location of lanes, lane width and traffic situation integrated.