Abstract: The phases of mutual-coupling and transduction coefficients in coupling-of-modes are essential parameters for accurately design of surface acoustic wave devices with electrode width control,distributed acoustic reflection transducers or natural single-phase unidirectional periodic structures.The traditional method of the phase extraction requires to separate calculation of the standing wave field,which involves the derivation and calculation of the complicated bulk wave contribution.Thus,the single cell model of periodic grating is established in finite element software COMSOL.The harmonic response solver is utilized to calculate the standing wave field at the edge of stop band.By determining the position of the standing wave nodes,the accurate phase extraction is realized.Specifically,our results agree well with the earlier reported ones.The correctness and effectiveness of the method are verified.After accurately extracting the phase parameters on (0°,138.5°,26.6°) langasite cut with heavy metal gold electrodes,which is widely used in high-temperature applications,the natural single-phase unidirectional transducer effect is suppressed.One-port surface acoustic wave asynchronous resonator is designed.Our simulation results coincide with the experimental results.