A new method and system for high precision measurement of sonar signal transmission time is presented.With double GPS high precision timing module

the method can realize the emission and receiving synchronization of the sonar signal.And in this measuring system

by employing the structure of separate emission module and receiving module

the receiving module can receive the acoustic signal directly and the transmission time can be measured precisely through the time difference of the emission and the receiving sonar signal.The proposed method can overcome the problem of big measurement errors produced by distorted echo signal because of obstacle in the traditional measuring method.Applying MCU C8051F020

the system can control the receiving of the sonar signal and measure

the transmission time via programmable logic device（PLD）.The experiment results show that the system has a stable performance and high measurement precision up to 5

8

μs.