Accurate mass data of transuranium nuclei is particularly important for the study of superheavy nuclei and the investigation of "island of stability". A low energy mass spectrometer to provide high-precision mass measurement and isobaric separation of short-lived fusion-evaporation reaction products is planned at the Spectrometer for Heavy Atom and Nuclear Structure (SHANS). A multi-reflection time-of-flight mass analyzer for SHANS has been designed and constructed and is being tested now. In the in-trap-lift mode, the latest simulation results by using SIMION give a maximal mass resolving power of 1.6 x 10(5) for a TOF of 6.4 ms, and the preliminary test results by applying the simulated voltages show that its mass resolving power has reached approximate to 7000 for a TOF of 1.6 ms.