The invention discloses a multi-point on-line detection device for coal mine gas based on spectral absorption, and relates to a coal mine gas detection device, in particular to a multi-point on-line CH4 concentration monitoring device based on a characteristic absorption line of methane (CH4) near a near infrared band 1653nm. The device comprises a D / A conversion module, a DFB laser, a 1*N optical splitter, an open air chamber group, a reference air chamber, a photodetector group, a preamplifier group, an electronic switch, a band-pass filtering circuit, a first phase-locked amplification circuit, a second phase-locked amplification circuit, a first A / D conversion module, a second A / D conversion module, a first DDS, a second DDS, a third DDS, an MCU, a display, a serial port, and a computer. Compared with the prior methane gas monitoring device, the device has the advantages of higher sensitivity, higher gas identification ability, quick response ability, extremely strong anti-jamming ability, easy network formation, and so on, so the device is a gas monitoring device which is most suitable to be used underground at present.