Abstract: To solve the technical problems of the axial load measurement of in-service bolts, the measurement system for the axial load of in-service bolts using the electromagnetic acoustic transducers is developed according to the principle of axial load measurement based on mode conversion. It consists of electromagnetic acoustic transducer, host, and software. Laboratory and field experiments indicated that the system could be used in axial load measurement of in-service bolts and the measuring relative error was less than 10%. The advantage of the system is that the electromagnetic acoustic transduction is adopted to obtain the good stability and to avoid the effect of couplant in the traditional piezoelectric transduction. In the meanwhile, a new technical means for the bolt axial load control is also provided.