Modulation Transfer Function(MTF) is an important imaging quality indicator of optical system, in order to evaluate the
imaging quality for a space remote sensing TDICCD camera, the MTF testing system，including hardware components
and software components, was established based on refocusing system. Firstly, the design of Three Mirror Anastigmatic
(TMA) optical system and the long interlace assemble TDICCD focal plane were introduced. Secondly, the construction
and the schematic diagram of the refocusing system was presented in detail, as well as the relationship between
refocusing range and position encoder for interlace assemble TDICCD focal plane. Thirdly, the schematic diagram of the
MTF testing system was given, and the relationship between MTF and contrast transfer function(CTF) was discussed.
Finally, on the basis of the schematic diagram of CTF, the transfer process of a square wave target was investigated. The
testing results indicate that the MTF testing system can measure the CTF of every TDICCD on the focal plane in the
focusing range, which meet the requirement of evaluation of imaging quality for a space TDICCD camera.