To accurately simulate the characteristics of continuously reinforced concrete approach pavement (CRCAP), a simplified concentrated spring model was proposed according to the force-deformation curve and the damage level of the CRCAP. Based on this, a dynamic finite element model of a semi-integral fully jointless bridge (SFJB) was established with SAP2000. The Modal analysis and Time History analysis were carried out on both the SFJB and the continuous girder bridge (CGB) for comparison. The sensitivity analysis of seismic performance was also investigated. The results indicate that the seismic response of the SFJB is only 24%~35% of the CGB in the low seismic fortification intensity zone, which can greatly enhance the seismic resistance of small and medium bridges.