The intrusion detecting equipment using laser has special advantages such as far detecting distance,but also exist shortages that easy to disturb by interfere light or small objects to cause false alarm.This article adopt chip NE555 and ADP3334 working together to offer modulate steady pulse of current to 808nm semiconductor laser diode,produce special frequency high stabilization laser in transmit port,the take-over port filter the waves of corresponding frequencies,detector have anti-jamming ability to interferential light such as sun ray or lamplight.Take-over port adopt amplifier OP295 to implement limit extent amplify,detectors can accurately working without adjustment in detect distance change from several meter to hundreds meter.SCM is used to control lower limit timer which relate to touch off alarm,and effectively decrease incorrect alarms from small objects′ disturb.