The promoting function of transportation to national economy generates from two sources, the one is the direct function to economy coming from the development of transportation itself, and the other is the indirect function to economy coming from the development of connecting industries because of the transportation growth. This paper uses the connection coefficients to describe the connection between the transportation and its connected industries, and uses the connection coefficients and contribution ratio of growth value to calculate the pulling and pushing function from the transportation to the national economy for Beijing. The research conclusion is that economic function from any industry depends on not only the size of its direct function to economy, but also its indirect function to economy. The size of function to economy depends on its position in the industrial chain, the connecting degree with pillar industries and the distance from transportation to pillar industries. If its position is in front of others, the pulling function is smaller than its pushing function, if it is in behind of others, the pushing function is greater than its pulling function. As a basic industry, the position of transportation is in front of other industries relatively, so its forward pushing function is larger than its backward pulling function.