In view of the many shortcomings of the existing rainbow and neon demonstration devices，combined with the optical principle，a new demonstration device for rainbow and neon reappearance is designed by using the physical phenomena of light refraction，reflection and dispersion．By placing one or two reflectors in the water tank，the light can be controlled to reflect once or twice in the water，and then refract out of the water，producing dispersion and forming clear rainbow and neon phenomena．The device realizes the reappearance of rainbow and neon and the quantitative study of influence factors．It has the advantages of simple structure，simple operation and obvious phenomenon． Through the demonstration of the device，students can better understand the optical phenomena in the atmosphere and the formation principles and laws of rainbow and neon．