The standard for assessment of prefabricated architectural engineering is relatively perfect, while the standard for assessment of prefabricated bridge has not been formally issued. The assessment system of bridge is quite different from that of architectural engineering, which cannot be directly applied. Based on the current research results of bridge engineering assembly rate calculation, the selection of assessment indexes and the selection of weight coefficients are systematically studied. The recommended calculation formula of urban viaduct assembly rate is obtained. Based on the calculation of assembly rate of several bridge projects in Wuxi, the assessment criteria of prefabricated bridge are put forward. The method of calculating the assembling rate of urban viaduct is studied in order to promote the further popularization and utilization of the prefabricated bridge.