The development of spatial spectral imaging technology makes the integration of detector array and light splitting elements become a trend. The long line array splice integrated filter (LLASIF) is the key device of spatial multispectral imager to realize concentrated light splitting at focal plane, and it has obvious demand in the spatial multispectral imaging system in China. In this paper, a 4-channel short/medim infrared LLASIF was designed. The narrow band filter of each channel was prepared by electron gun evaporation method assisted by ion beam. The splicing process was explored by using specially developed tools and the LLASIF was developed. The test results show that the average transmittance of each narrow band filter reaches 90%, the minimum bandwidth is 230 nm (central wavelength is 4.95 μm), and the spectral performance is consistent with the design results and meets the performance requirements. The minimum seam width is only 10 μm, the seam parallelism error is 1 μm. The integrated filter structure and splicing strength can withstand the vibration resistance test. The integrated filter has been successfully applied in space optical remote sensing instrument.