Based on the scanning grating mirror we developed, this paper presents a method of the precise control of a scanning grating mirror and of high-speed spectrum data detection. In addition, the system circuit of the scanning grating mirror control and spectrum signal detecting is designed and manufactured in this paper. The mirror control system includes a drive generator module, an amplitude detection module, a feedback control module, and a variable gain amplification (VGA) module; the detecting system includes a field programmable gate array (FPGA) main control module, a synchronous trigger module, an analog-digital conversion (ADC) module, and a universal serial bus (USB) interface module. The final results of the experiment show that the control system has successfully realized the precision control of the swing of the scanning grating mirror and that the detecting system has successfully realized the high-speed acquisition and transmission of the spectral signal and the angle signals. The spectrum has been reconstructed according to the mathematical relationship between the wavelength λ and the angle β of the mirror. The resolution of the spectrometer reaches 10 nm in the wavelength range of 800⁻1800 nm, the signal-to-noise ratio (SNR) of the spectrometer is 4562 at full scale, the spectrum data drift is 0.9% in 24 h, and the precision of the closed loop control is 0.06%.