The invention provides an assembling method and system of a railway hopper car. The provided assembling method for the railway hopper car comprises the steps that according to user requirements, product functions and target parameters are obtained; then the design volume is obtained, and car body structure parameters are determined; according to the product functions, a part module is obtained from a module library; and the target size of the part module is determined according to the obtained parameters, the part module is adjusted to the target size and assembled, and assembling of the railway hopper car is efficiently, quickly and conveniently completed. Repeated work for similar parts is avoided, and the production period is shortened.