Scattering phase function of wake bubble films is obtained based on Mie theory and the distribution model of ship wake bubbles. Using the function the backscattering signal of bubble films is simulated by Monte Carlo method, which is useful to detect and analyze the backscattering signals of ship bubble wakes in situ measurement. The analyzsis of the scattering phase function and the backscattering signal characteristic in different regions of ship wake, shows scattering phase functions of bubble films in different wake region change little and affect the signal tinily; the variety of bubble density which causes the variety of multiple scattering and the bubble attenuation coefficient is the dominating reason influencing the backscattering intensity. Multiple scattering intensity becomes stronger when the bubble film is thick. When the thickness of bubble film is larger than a given times of attenuation length, the backscattering signal changes little with the increase of bubble film thickness.