Optical compressive spectral imaging method is a novel spectral imaging technique that draws in the inspiration of compressed sensing, which has the features such as reducing acquisition data amount, realizing snapshot imaging for certain scenery, increasing signal to noise ratio and so on. Considering the influence of the sampling quality on the ultimate imaging quality, matching the sampling interval with the modulation interval in the former reported imaging system, while the depressed sampling rate leads to the loss on the original spectral resolution. To overcome that technical defect, the demand for the matching between sampling interval and modulation interval is disposed and the spectral resolution of the designed experimental device increases more than threefold comparing with that of the previous method. Optimization method is improved and a variation term that represents the spectral-dimension continuousness of the data is added to the regularization function, which enhances the controllability and reliability for the data reconstruction. Result proves that the spectral channel number increases to a great extent effectively, the average spectral resolution reaches 1 nm, and the spectral images and curves are able to perform the spatial and spectral character of the target accurately.