The emergence of highly maneuverable weak targets has led to a serious degradation or even failure of traditional radar detection. In this paper, a coherent accumulation algorithm based on combination of scaling algorithm(SA) and discrete polynomial-phase Transform(DPT) is proposed in terms of the calculation burden and detection performance, which can, firstly, perform fewer times of speed parameter compensation based on SA for the transmitted signal; secondly, use segmented FFT to estimate the time delay range of the target initial distance for the echo signal, and then use the DPT algorithm to complete the parameter estimation such as target speed and acceleration within the estimated time delay unit, while analyzing the effects of the number of segments, compensation speed and delay unit on the detection performance, and giving out the output SNR and the amount of complex multiplication of the proposed algorithm. Finally, the proposed algorithm has been verified by experimental data for its effectiveness in accumulation gain and parameter estimation. This method is for sub-optimal estimation, requiring much less computation than full-parameter search methods, but performs better than non-parametric search methods in detecting weak signals.