In order to analyze the shrinkage, creep effect of the old and new concrete beam after small and medium-sized span concrete slab bridge was broadened, slab beam was taken as an example, and the vertical stress of the old and new beam caused by beam body shrinkage and creep effect was analyzed, and the influence of the different construction conditions on the vertical stress of cement slab was compared by making use of different calculation methods.At the same time,the redistribution of the stress at the juncture caused by the different shrinkage, creep of the new and old concrete beams because of the time difference was analyzed. The analysis results show that the longitudinatensile stress on the new beam caused by shrinkage and creep may lead to longitudinal crack of new beams.