The invention discloses a pre-projection raycastingvolume renderingparallel processing method. The following steps are included in the volume rendering data handling procedure: calculating bounding volume of a three dimensional volumetric model; projecting the bounding volume in the screen space; storing the corresponding coordinates of a projection area; and conducing the parallel processing of volume rendering data. The method adopts the parallel processing manner of pre-projection, so that all the computing nodes do not need to wait for all tasks to be calculated and finished and then transmit the result data to a main node without waiting, and instead, the computing nodes send intermediate result data to the main node immediately after a task block is calculated and start the calculation for the next task block. Fewer task blocks are distributed to the main node at first. The method provides the optimum estimation for the number of task blocks distributed to each computing node, thereby greatly reducing the processing volume of data and improving the processing speed of data.