The utility model discloses a stealthy burglar alarm mainly relates to the motor vehicle theftproof and equips technical field. Including power, buzzer and casing, set up time relay and auxiliary relay base in the casing, cartridge auxiliary relay on the auxiliary relay base, set up the wire guide on the casing, casing outer one is served and is set up button switch, the outer other end of casing sets up mercury angle switch, set up the fixed bolster on the mercury angle switch, the casing is fixed on the motor vehicle, still includes isolator. The utility model has the advantages of it is simple that it has the installation, easy maintenance, and the cost is low, and disguised strong characteristics can avoid burglar alarm to be destroyed, and the interference killing feature is strong to can direct control starter controller, report to the police during motor -driven chefei normal boot, alarm device destroys the back motor vehicle and can not start, can solve the motor vehicle problem of losing by fundamentally.