The utility model relates to a controllable transmission of luminous flux probe solves the problem that the luminous flux can not conveniently be adjusted along with the change of the liquid turbidity that awaits measuring to the transmission probe. This device sets up light source interface, transmitted light interface respectively including probe shell, the both ends of probe shell, is provided with the transparent sample cell in the probe shell between light source interface and transmitted light interface, is provided with automatically controlled light ring between sample cell and the transmitted light interface, still is equipped with the control signal interface of connecting automatically controlled light ring on the probe shell, the outside connection director of control signal interface. Automatically controlled light ring can change the light ring size under external voltage's control signal to change the luminous flux of transmitted light. The utility model discloses a transmission probe luminous flux controllable can the convenient voltage control that pass through changes the luminous flux under the widely different circumstances of liquid turbidity awaiting measuring, can insert computer system realization luminous flux automatic adjustment, reduces to adjust the influence of spectrophotometer integration time to the system.