Precise extraction of coupling-of-mode (COM) parameters plays a key role in the design for modern high performance surface acoustic wave (SAW) filters. An accurate and efficient analysis of char- acteristics for SAW propagating under periodic metal gratings has been developed based on the concept of harmonic admittance and periodic Green抯 function. Some further improvement is made on the nu- merical algorithm, such as isolation of the logarithmic singularity, asymptotic simplification of periodic Green抯 function, and utilization of Chebyshev polynomials as basis functions of the charge distribution. The most important point is extraction of the phase of coupling reflection coefficient by the characteris- tics of standing wave on the edges of stopband. This approach leads to a fast, precise and full extraction of COM parameters. The results and discussions for several materials have been presented. Precise extraction of coupling-of-mode (COM) parameters plays a key role in the design for modern high performance surface acoustic wave (SAW) filters. An accurate and efficient analysis of char- acteristics for SAW propagating under periodic metal gratings has been developed based on the concept of harmonic admittance and periodic Green’s function. Some further improvement is made on the nu-merical algorithm, such as isolation of the logarithmic singularity, asymptotic simplification of periodic Green’s function, and utilization of Chebyshev polynomials as basis functions of the charge distribution. The most important point is extraction of the phase of coupling reflection coefficient by the characteris- tics of standing wave on the edges of stopband. This approach leads to a fast, precise and full extraction of COM parameters. The results and discussions for several materials have been presented.