The invention discloses a warning device used for transparent glass in hotel lobbies. The warning device comprises a No.1 rectangular base, wherein a telescoping mechanism is arranged in the No.1 rectangular base; an adsorbed fixing mechanism is arranged on the rear surface of each rectangular shell; a voice prompt mechanism is arranged in each rectangular shell; a night warning mechanism is arranged outside each rectangular shell; the voice prompt mechanism is jointly formed by an infrared body sensor, a wireless module, a timer, an infrared distance meter, a data access device, a temperature and humidity sensor and an intelligent voice module, which are arranged on a rectangular bearing plate; a controller is arranged on the lateral surface of each rectangular shell, is electrically connected with each storage battery and is electrically connected with each voice prompt mechanism and each night warning mechanism respectively. The warning device has the beneficial effects of simple structure and strong practicability.