Abstract: The quantitative performance analysis of overlap averaging method is given for the first time in this paper. As result of the analysis, the mathematic formula of detection probability was derived. From mathematic deduction, it was revealed that the sensitivity deterioration couldn't be ignored when the overlap averaging method was used to speed up the search. Specifically, the sensitivity deterioration would be about 3 dB when the number of overlap averaging points was doubled. To be able to still work in low SNR environment, some compensation measures should be taken for overlap averaging method. A new measure of taking frame head to assist acquisition was proposed. The overlap averaging method with frame head assistance could improve accumulation gain because it extended the correlative integration time simply. Monte Carlo simulation has been implemented. The results show that the accuracy of derived mathematic formula is satisfied and the performance of frame head assisted overlap averaging method is good. The detection performance of 4 ms integration using eight-point overlap averaging method is almost the same as that of 2 ms integration using two-point direct averaging method, while the amount of data processing is reduced by half.