The invention relates to a light emitting device and a control method, comprising: a light emitting unit, a constant current driving circuit, and a controller; at least two light emitting units are connected in series to the constant current driving circuit, and the light emitting unit includes a light emitting branch and a bypass branch , the light-emitting branch and the bypass branch are connected in parallel, there is a light emitter on the light-emitting branch, there is a switch on the bypass branch, the switch has a signal input terminal, the controller has a signal output terminal, and the signal input terminal is connected to the signal output terminal, The controller is used to control the on and off of the switch. Using a single constant current drive power supply to supply power to multiple light emitters has a simple structure and is easy to control. By controlling light emitters with different light colors, the light emitting devices can be precisely controlled to present different colors.