The GJG100J laser methane sensor for mines is used to monitor the concentration of methane gas in methane drainage pipelines on the ground and underground in coal mines. It is dedicated to the monitoring of gas drainage of pipelines, which can be directly installed in a gas drainage pipeline. It is able to work stably and not affected by water and impurities in pipelines. It can also locally display the methane concentration and automatically convert the methane concentration into a standard electrical signal and transmit this signal to related equipment.