The transmitter is one of important upper-air sounding instruments.A volume tube as a key element of the transmitter has been used for a long period,it has become a reality that the volume tube is replaced by a transistor in the transmitter.The transistor transmitter Type GPZ5-3 has been used in all upper-air sounding stations since the beginning of 1997.The information of this instrument including its principle,specifications test and the right operation was described.