Abstract: The problem of estimating time of arrival(TOA) of complex sinusoid with rectangular pulsed envelope is considered.In the absence of a prior knowledge for the signal parameters(amplitude,phase and frequency),the coarse estimation of the start position and end position by correlation detection is performed at first.Consequently,the received signal is transformed to baseband one with the estimation of the frequency.The start position of the signal can be effectively extracted by locating peak magnitude of the wavelet transformation of the baseband signal.The principles of wavelet scale selection are discussed and the Cramer-Rao low bounds(CRLB) for TOA estimation is derived.The performance of the estimator is investigated through simulations,and the results show that the method is efficient for fine estimation of TOA.For SNR=6 dB,the root mean square is less than 0.8 times sample interval.