At present, in some fields, such as metal wound detection and biomedical, the signal acquisition technology mainly focuses on occasional signal.If the traditional fixed-frequency signal acquisition method is used, it will cause a serious waste of storage resources.To solve this problem, a sampling method based on DDS clock phase synthesis is proposed.The method combines DDS technology and waveform phase synthesis technology and adaptively switches the sampling frequency according to the signal characteristics.While ensuring the integrity of signal information, the data storage of useless signals is reduced. Through simulation and experiment results show that the method on FPGA platform is well on achieving the sampling rate of 12 MHZ and 96 MHZ real-time switching control, a complete reduction of the highest frequency of 10 MHZ waveform detection details, at the same time under the parallel processing of the FPGA using split phase synthesis by sampling rate of at least four times, optimize the resource utilization.