A design principle of LED features detection equipment based on micro fiber optic spectrometer is introduced. To reduce the self-absorption error caused by measuring luminous flux from integrating sphere and the error of LED luminous flux caused by temperature increasing, the LED is placed with the detector into 90° to solve the problem. Meanwhile, in order to achieve the goal of miniaturization high-resolution, the fiber optic spectrometer module uses non-symmetrical cross Czerny-Turner spectral structure. A design of the adjustable constant current source is purposed based on the influence of LED luminous flux by forward current. The results show that the research has certain guiding significance in developing micro LED features detection equipment. Since the constant current source is adjustable and can be displayed, the influence of LED optical features by current changing can be clearly observed.