This paper advances a scheme using the TMS320C62x to realize a digital pulse compression system which waveform is linear FM signal.The finite register effects in the system are discussed.The word length errors using truncation of sign magnitude code are analyzed.And the computer simulations which uses truncation and ronding of sign magnitude code and complementary code are given.The improvement of finite register length effects by noise is discussed.The paper also raises an effective method to solve the word length error′s problem.