The invention provides an intelligent vehicle-mounted child security device. The intelligent vehicle-mounted child security device comprises a sensor module and a controller module; the sensor module comprises a sensor front cap, a sensor rear cap, a temperature sensor, a microwave sensor module, an infrared sensor module, a first processing unit, and a first wireless communication unit; the controller module comprises a controller front cap, a controller rear cap, a second processing unit, a second wireless communication unit, and a third wireless communication unit. When the temperature sensor detects that in-car temperature reaches the set upper limit, the infrared sensor is started; when the detection result shows that a child is left in the car, the car whistles, and meanwhile, the microwave sensor is started to conduct comparison detection; when the comprehensive detected result shows that the child is in the car, a car air conditioning system is started for cooling, alarm information is sent out to an assigned mobile terminal, and a car lighting system is turned on to flicker and a whistle system is turned on to whistle to give an alarm to people around the park car.