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Sealing performance is one of the key technical parameters for spacecraft in orbit. The pressure change leak detection method is the important technical way for protecting the spacecraft cabin from leak. For the mini-integration and high precision requirements of spacecraft leak testing equipment, a minitype pressure change leak detector is designed and developed. DSP was used as the core data processor, and the absolute pressure and the differential pressure leak testing methods were analyzed. The interface based on 485 was designed to sample the absolute pressure sensor signal and using 250Ω high precision resistance into the current loop, the differential pressure sensor signal was transformed and the signal was sampled by the ADS1247 with 24bit AD.And then two temperature sensor based on heat resistance were sampled with constant current supply and resistance comparing method.And these signals were processed by the DSP, and the leak rate value was gained and displayed on the LCD. The leak detector was designed, which could measure absolute pressure, difference pressure and temperature at the same time, and then the precision and leak testing ability were met the requirements. The study results show that the instrument has simple facilities, the high precision and high reliability. It can measure the pressure, temperature, leak rate parameters at the same time. The leak testing max relative error is 19.3%, and the relative uncertainty is less than 2%,it can be better applied to spacecraft leak detection.