Rainbow is a common atmosphere optical phenomenon. In certain weather conditions, additional color arcs may appear near the main rainbow, which are called supernumerary rainbows. So far, there are few reports on the experimental research of the supernumerary rainbows. In this paper, we study the supernumerary rainbows from two aspects of both the collective scattering and individual scattering. The supernumerary rainbows phenomenon was reproduced by water mist light scattering, and the influence of the size and distribution of the water drops on the supernumerary is discussed. Then, through the light scattering experiment of single water drop, the phenomenon of supernumerary rainbows under different illumination wavelengths and different water droplet sizes is studied, and the formation mechanism of the supernumerary rainbows is explained from the micro level. We also use the Mie scattering theory to calculate and study the influence of the droplet size and its statistical distribution on the supernumerary rainbows phenomenon, and the calculation results further are consistent with the experiment ones.