The combination of lens and pinhole limits the enhancement of the laser output power in the high-power laser system. Low-pass spatial filter without focusing can surmount the drawbacks of the pinhole filters. The low-pass spatial filters based on multilayer dielectric film are analyzed and their filtering performances are validated. The non-focusing low-pass spatial filter is successfully explored to substitute for the focusing one. The design method is based on phase-shifted Rugate thin-film spatial filter, narrow bandpass filter and the combined device of long-wave-pass and short-wave-pass cutoff filters, and the angular spectrum bandwidth of bandpass filter are up to submillimeter radians. We mainly discuss three design methods and point out their advantages and disadvantages to find out the best one. The experimental results show that the effects of random and system error during depositing the filter is mainly responsible for the deviation of the designed and measured values.