The invention provides an image ratio constant flow source circuit driving a multipath light emitting diode, belonging to the electronic technical field. The circuit structure comprises a pedestal generation circuit (11), a low-pass filter circuit (12), a V/I0 conversion circuit (13), a multipath image ratio constant flow source circuit (14) and a switch control circuit (16), wherein the image ratio constant flow source circuit (14) comprises transistors (Q10, Q11, ... Q1n), Light Emitting Diode loads (D10, D11, ... D1n), ratio resistors (R10, R11, ... R1n) and a sampling resistor (R0); the switch control circuit (16) comprises a third resistor (R3) and a fourth transistor (Q4), and completes control action by a digital signal (Di). The circuit of the invention leads illumination intensity of the multipath light emitting diode to be stable, can obtain continuous spectrum or modulated spectrum, has convenient use, low cost and electricity conservation, and is convenient for portable instrument use.