Starting from the trend of high speed rail development and taking the Nanjing-Shanghai section of Beijing-Shanghai high speed rail line for example, this article analyzed the tractive, braking and running resistant characteristics of high speed train by way of computer simulation. A brief calculation and comparison on socio-economic effect were made including runing speed, travel hours and traffic capacity of various trains at the speed between 180 km/h to 500 km/h. In addition the energy consumption of trains at different speed was compared .The proposal concerning the reasonable speed level of high speed rail traffic under the existing conditions was made.