在放射性环境样品以及其它微弱放射性样品的测量工作中,低本底β测量仪是必不可少的常规测量仪器。本文所阐述的仪器是采用塑料闪烁体作反符合环,灵敏直径为20mm的金硅面垒型半导体探测器作主探头,使仪器的本底降至0.122±0.04cpm, 对于~(90)Sr-~(90)Y的探测效率达到48.1％。 In the radioactive environmental samples and other weak radioactive sample measurement work, the low background beta meter is an essential conventional measuring instrument. The instrument described in this paper is a plastic-scintillator anti-coincidence ring, a sensitive diameter of 20mm gold-silicon surface barrier type semiconductor detector as the main probe, the instrument’s background dropped to 0.122 ± 0.04cpm, for the (90) Sr - ~ (90) Y detection efficiency of 48.1%.