Abstract: Computerized tomography (CT) forward projection is a simulation of CT data acquisition, which can not only be used to produce projection data, but also is a key part of the iterative algorithms for CT image reconstruction. The forward projection requires both excessive computation and time consuming in cone-beam scanning mode. For improving traditional forward projection algorithms, a graphics processing unit (GPU) based cone beam CT forward projection algorithm is proposed. The algorithm generates forward projection image rapidly by calculating the projections on detector of all X-rays in parallel. Since the algorithm supports the calculation at full floating point precision and adopts tri-linear interpolation, the high-precision projection image can be achieved. The advantages of this algorithm were verified by the experiments of the projection calculation of Shepp-Logan phantom and by the comparison with other forward projection algorithms.