The utility model discloses a hidden automobile burglar alarm, including chip IC1, relay K, speaker B and solenoid valve A, chip IC1's pin 1 connecting resistance R1, power VCC, relay K's contact K -1, chip IC2's pin 4 and chip IC2's pin 8, chip IC1's pin 2 connecting resistance R1, electric capacity C1, chip IC2's pin 2 and chip IC2's pin 6. The utility model discloses simple and easy electron lie detector circuit structure is simple, components and parts are few, utilize microwave doppler effect, carries out electronic monitoring through the induction field, triggers for traditional infrared ray, gate formula, and it is disguised strong, is difficult for explaiing, when the vehicle is stolen, can send humanized audio alert, breaks off the oil tank fuel feeding simultaneously, prevents that the vehicle is stolen, has consequently that the disguise is good, the function is various and convenient to use's advantage.