The invention belongs to the field of coal mine safety monitoring devices, and particularly relates to a coal mine underground roadway ventilation alarm device. The coal mine underground roadway ventilation alarm device comprises a ventilation detection unit, a poisonous gas detection unit, a dust detection unit, a human body detection unit, a microprocessor, an alarm unit and a wireless communication module; the poisonous gas detection unit is used for detecting the concentrations of methane, CO, NO2 and SO2 inside an underground roadway in real time; the dust detection unit is used for detecting the concentration of dust inside the underground roadway in real time; the human body detection unit is used for detecting whether a person exists or not; and the wireless communication module is used for sending detection results to a monitoring center and a mobile client. The coal mine underground roadway ventilation alarm device can achieve automation and intelligence of a mine ventilation system, starting and stopping of a standby draught fan are automatically controlled according to the underground gas concentration, the ventilation capacity in the roadway is ensured, and thus the requirements for safe production and reliable operation are met; and meanwhile, alarms of different kinds of voice can be automatically given out according to the out-of-limit conditions of various related important monitoring indexes.