A high temperature bolt stress monitor, based on the testing of the Transit Time of Lo ngitudinal Wave and Shear Wave (TTLSW for short) and on the calculation of the stress through the established stress vs TTLSW equation, has been developed and tested. Lithium Niobate was used for piezoelectric material, gold or silver films were used for coupling material an clamping together method was used to install the transducer. Time interval areaging, zero crossing detect and several other techniques were used to improve the accuracy of TTLSW measurement. Using this method within the range of 30-360℃, and 0-443MPa the accuracy of stress is better than 9.8MPa.