Radar data acquisition and storage equipment is an important equipment in radar system. It provides an effective method for off-line processing of Time of Arrival(TOA) of measured echo signal in engineering implementation. In this paper, the actual echo signal in radar acquisition and storage equipment is analyzed, and the TOA of Pulse Repetition Interval(PRI) detection method based on adaptive double-threshold is proposed, which can realize TOA detection of PRI in any echo data segment of time-sharing systems with a detection speed about 11ms. The TOA detection of Synthetic Aperture Radar(SAR) target echo based on sliding window method is proposed. The TOA of SAR target echo is effectively detected and verified by simulation.