A real-time imaing nonuniformity correction algorithm on a Field Programming Gate Array(FPGA) platform was proposed to modify the imaging nonuniformity of a multi Time Delay Intration(TDI)CCD mosaic camera. Firstly, the definition of Photo Response Nonuniformity(PRNU) and its generation in the multi-TDICCD mosaic camera were introduced. Then, the synthetical correction algorithm was presented, in which the two-point correction method was used in a single channel, gain averaging correction method among multi-channels and the scene-adaptive correction method among multi-TDICCDs. By considering the reliability and the influence of finite word-length of the FPGA, the synthetical correction algorithm was optimized and implemented on the signal processing FPGA platform. Furthermore, a scheme for modifying correction factors and spaceborne calibration were given. The experimental results indicate that the imaging nonuniformity can be decreased from 4.82% to 0.27% for a single TDICCD, and to 0.41% for a 3-TDICCD mosaic camera with the proposed correction algorithm.It also proves that this correction algorithm has high real time performance, good practicality and efficiency, and satisfies the requirements of target projects.