A linear current-pulse discriminator consisting: of a transistor monostable multivibrator and a Si tunnel diode is described. The input currant pulse range is about 50$mu$A~5.23mA. The measured maximum linearity deviation is $pm$0.75% in the input current pulse range mentioned above. The pulse resolving ability of the discriminator measured depends upon the bias current through the T, D. ; and, under the reverse bias current of 3mA, the resolving time is 2rs if allow the excess pulse amplitude of 5%. The threshold stability of the discriminator depends mainly upon the stability of the peak current Ip of the T. D. ; and, under the ambient temperature variation from $0^{circ}C$ to 5$0^{circ}C$, no bigger threshold variation than the maximum linearity deviation, i. e. $pm$ 0.75%, was observed.