Aiming at the needs of high time resolution imaging in low light environment, based on CIS process, a large-size PPD pixel device with ultra-fast charge transfer is designed and simulated, which owns a gradient-doped triangular shape and central floating diffusion region. The doping shape and gradient doping of the N-buried layer can enhance the gradient potential formed on the transmission path, thereby the transfer of the photo-generated charge from the Nburied layer to the charge storage area will be accelerated. At the same time, by making the gradient doping of the transfer transistor channel, the rebound charge is reduced and the transfer efficiency is effectively improved. Simulation results show that the charge transfer time is 1ns and the rebound charge level is below 1e- when the triangular branch-shaped circular pixel device contains 30,000 charges and the charge transfer efficiency reaches 99.9%. Thus, the PPD pixel device can be used for high time resolution imaging in low light environment.