Lightweight vehicle bodies have become the development trend in auto industry, so the self-pierce riveting (SPR) technology has attracted extensive attention. This paper proposes a novel control approach of the flexible servo riveting gun based on SPR technology. First, this paper briefly introduces the riveting procedure based on the mechanical structure of servo riveting gun. Then the riveting quality inspection rules of traditional riveting guns are used for reference to plan the force-position curve in riveting process autonomously, and the cubic spline curve is adopted to construct the force trajectory. To control this planned force trajectory, riveting force measured by sensor is fed back into the closed-loop control. According to the deviation between theoretical and actual riveting force, the set value of riveting speed is changed based on admittance control algorithm, so the servo motor’s torque is indirectly controlled to make the riveting force reach the set value. Finally, the control approach is applied to the servo riveting system designed by our lab. Riveting results show the feasibility of proposed control approach.