With the development of industrial automation, the technology of safety instrument & system is paid more and more attention, while the research on safety instrument & system in our country is still in its infancy. This paper put forward to the safety structure of the Digital Level Transmitter, mainly studies the functional safety of the digital level transmitter, FMEDA analysis, software selfdiagnosis technology, V&V and software testing, and achieved SIL2 certification of the digital level transmitter. It is the first digital level transmitter in the domestic that achieved the SIL2 certificate by Rhine TUV, which break the technological monopoly of longterm safety instruments and systems by foreign countries.