In this paper, a nonlinear proportional derivative control (NPD) is proposed to solve the trajectory tracking problem of a parallel Delta robot. In order to handle the strong coupling effect and external disturbances as well as to realise high-precision trajectory tracking, the proportional and derivative gains are adapted through time using the tracking error and its time derivative respectively. Experiments are carried out on the parallel Delta-4 robot, and it is shown the effectiveness and the superiority of the NPD controller over the fixed gains PD controller.