Shrinkage and creep may increase the deflection of concrete composite beams and therefore affect the mechanical properties of components. In order to investigate the increase pattern of the deflection of concrete composite beams under action of shrinkage and creep, a calculation method for the deflection of concrete composite beams induced by shrinkage and creep was established. The comparison between the proposed method and numerical simulation indicates that the results obtained by the two methods are consistent. Based on this method, the sensitivity of loading age and stress level of concrete composite beams was analyzed. The results show that the deflection of concrete composite beams varies with the loading age when the stress level is different. When the stress level is low, the deflection increases with the loading age, whereas the deflection declines with the rising of loading age. Differential creep at the overlap surface of concrete composite beams is much smaller than the differential shrinkage, and the deflection caused by the difference of the precast concrete and cast-in-place concrete at the overlap surface is mainly caused by difference of shrinkage.