Abstract: The estimation accuracy of time difference of arrival(TDOA) is determined by the frequency distribution and energy of signal and noise. Multi-carrier signals have broad distribution in frequency domain, the problem of low estimation accuracy for TDOA of single carrier signal can be overcome through coherent integration to improve the use of efficient bandwidth and energy. Focus on the TDOA estimation problem of multi-carrier baseband signals, this paper first analyzed the cross correlation function(CCF) of single carrier signal, and the phase relation of baseband signal between carrier frequency and TDOA is investigated. Then the CCF of each multi-carrier signal is deduced, and the phase relation of each CCF is analyzed. Coherent integration is realized by phase compensation. The theory performance of TDOA estimation for multi-carrier signals are analyzed, and the influence of the signal parameters on TDOA estimate accuracy is derived. Monte Carlo simulations validate that the accuracy of proposed coherent integration TDOA estimation algorithm for multi-carrier signals exceed that of single carrier signal obviously, and the performance improvements accord with the theory analysis well.