The breakwater has poor protection against long-period waves，which can easily invade the harbor directly and worsen the operating conditions in the harbor.This paper relies on the physical model test results and the BW numerical model to study the generation mechanism of long-period waves in the harbor pool under the action of two-color waves.The BW numerical model is verified，and the model agrees well with the test results.Under the action of two-color waves with frequencies f1 and f2 respectively，nonlinear interactions occur between waves to produce waves with frequencies such as Δf，2f1-f2，2f2-f1，2f1，f1+f2，and 2f2.When the wave frequency Δf equals to the harbour natural frequency，the wave height of such wave frequency will amplify.The nonlinear interaction of waves is positively associated with the increment of wave height and tenability，which results in the increase of long-period wave height.