Dynamic interactions among wind power, photovoltaic (PV), and synchronous generators (SG) affect power system stability. The dynamic interaction mechanism and stabilization enhancement method in the wind/PV integrated power system are studied based on the sensitivity of the damping coefficient. First, the impact of the doubly-fed induction generator (DFIG) and PV generators on the transient response to the SG is determined using linearized expression. Secondly, the closed-loop transfer function of the DFIG/PV integrated power system is derived to analyze the dynamic interaction process among the DFIG, PV, and SG. The damping coefficients provided by DFIG and PV to SG are newly derived to quantify the impact of the DFIG/PV on power system oscillation. Then, an analytical expression for the sensitivities of the damping coefficients to the output of the DFIG/PV is proposed. It is used as the gradient information of the interior point method to improve power system stability by adjusting the outputs of the DFIG/PV. Finally, the simulation results verify that adjusting the output of DFIG/PV can improve the damping of dangerous modes of PV/DFIG and the stability of the system. The calculation efficiency and accuracy of the optimization method with sensitivity as gradient information are verified. The average amplitudes of the power angle with and without optimization are 25.1589° and 18.0165° respectively.