When the laser beam is incident into the soap films at a small angle，there will be a small branch of light which changes rapidly in the soap film．This phenomenon is called branch flow of light，also known as “light whisker”． The effects of the area of plane soap film，laser wavelength and laser intensity on the phenomenon of branch flow of light are investigated by experiments．The results show that the larger the area of soap film is，the more obvious the phenomenon of branch flow of light is; when the laser power is fixed，the green light with shorter wavelength is used as the light source，and the phenomenon of branch flow of light is easier to be observed than the red light; when the laser wavelength is fixed，the light intensity is stronger，the phenomenon of branch flow of light is more obvious．