Abstract: Pressure transmitter and differential pressure transmitter are widely used in the parameter measurement in research reactors, however the improper application will have negative effect on the safety of the process system and the safety of personnel and equipment. In addition, if the measurement signal is unreliable or the equipment fails, it may cause serious safety accidents and economic losses to the research reactors. In this paper, the factors and countermeasures that should be considered in the application of pressure transmitter and differential pressure transmitter are studied. It is proposed to design the primary instrument room and the reverse flushing system, and use the disassembly free method for instrument calibration in order to achieve reliable measurement and efficient maintains, thus to make sure the operation and maintenance of transmitter meet the requirement of safe operation and effective utilization of reactor.