To improve the spectral acquisition efficiency of the Liquid Crystal Tunable Filter(LCTF). A fast acquisition method which could be applied to the spectral imaging system was proposed. A better observation matrix was designed and constructed. Within the theoretical framework of compressed sensing, spectral super-resolution reconstruction was made possible and the feasibility of the method was verified by experiments. The results indicated that when the sampling rate of was 18.08% (sampling step length was 30 nm), the correlation coefficient between the reconstructed 4.81 nm resolution spectrum and the traditional full sampling spectrum was 0.91, the Peak Signal-to-Noise Ratio (PSNR) of the reconstructed super resolution spectrum was 99.63 dB and the acquisition speed was 5.53 times that of the traditional method. As long as the quality of spectral recognition is ensured, this method can facilitate fast and lightweight acquisition of spectral information, which can technologically contribute to dynamic target measurement and rapid detection while improving the applicability of LCTF spectral imaging technology.