A method for estimating channel impulse response (CIR) in a communication system includes converting RF analog signals to obtain baseband digitized signals, sampling the baseband digitized signals according to the symbol period or bit period, cross-correlating at least part of the samples and a predetermined set of training sequence symbols, and calculating the ratio of the maximum square of the modulus (power) value and the second largest value among the outputs of the cross-correlations. If the ratio is larger than a first predetermined value, the method outputs the cross-correlation values as the CIR according to the time step index of the maximum power value, and if the ratio is not larger than the first predetermined value, the method calculates the energy of a predetermined window and outputs the cross-correlation values as the CIR according to the time step index of the maximum energy.