PURPOSE: A method for vehicle theft preventing service and a system thereof are provided to detect vehicle theft of a movable vehicle without starting the engine. CONSTITUTION: An electronic key(102) outputs a suspected theft alarm message when receiving the suspected theft alarm message. A user terminal(108) outputs the suspected theft alarm message when receiving the suspected theft alarm message. A theft monitoring device(100) is installed on a vehicle and detects a separated distance from the electronic key. When the separated distance is greater than or equal to a predefined distance, the theft monitoring device determines a suspected theft state. The theft monitoring device transmits the suspected theft alarm message to the electronic key and the user terminal.
