In the shallow water of the Yellow Sea, filtering of mode 1 and mode 2, by employing a vertical array of nine hydrophones, has been realized in the frequency range of 250–800 Hz with a near isovelocity condition. Eigenfunctions of the mode were calculated by two parameters (P,Q) to describe the characteristics of bottom reflection approximately at small grazing angles. The advantage of treating the bottom in terms ofPandQrather than using the familiar sound speed, density, and attenuation coefficient is that the bottom reflection loss due to the effect of bottom roughness can be incorporated. Results of mode filtering were quite favorable. Group delay measurement of mode 1 and mode 2 agrees well with theoretical values calculated by a fitting value of the bottom reflection phase shift parameterP. The parameterQof the bottom reflection loss can be extracted from the amplitude ratio of mode 1 and mode 2. The extracted values ofQwere near those ofQobtained by other approaches.