The dynamical behaviors of onset patterns on the surface of viscous liquid in the large-aspect-ratio container under double-frequency parametric excitation have been investigated theoretically.The calculation shows the lower margin curves of exciting acceleration for pattern formation,the response modes and the frequency spectra of the pattern as well.Furthermore,the bicritical phenomenon found in the double-frequency Faraday experiments is also studied.All of the results from the theoretical calculation are in excellent agreement with those measured by Edwards et al. without any adjustable parameter.