Visual pipeline mechanism and basic structure of the parallel program were discussed based on the characteristics of Visualization ToolKit (VTK). Since the problem of visualization post-processing in computational fluid dynamics, VTK color mapping algorithm was introduced and a program of showing nephogram was written. In order to reduce the running time, a parallel algorithm was proposed. The proposed algorithm made full use of the parallelism between the VTK tasks, reduced the program running time and improved the running efficiency. Finally the speedup ratios of files of different sizes were compared and analyzed. The results show that the requirements of visualization post-processing is satisfied by visualization technology based on VTK and the good parallel effect is obtained with Message Passing Interface (MPI).