Based on microchannel plate (MCP) X-ray optics, a transmission soft X-ray band-pass approach is presented. X-ray transmission band-pass characteristics are given through three structures of MCP channel. Calibration results from a square hole MCP and filter on Beijing Synchrotron Radiation Facility show that MCP transmission spectrum is of a wide range of band-pass options and high efficiency, and can achieve multi-point design of 100 eV bandwidth at lower than 1 keV with different filters.