The invention relates to a method for synchronously and accurately measuring concentrations of various gases. The method comprises the following steps: emitting one beam of pump light into a first resonant cavity to form first detection laser; emitting the other beam of pump light into a second resonant cavity to form second detection laser; directly transmitting the first detection laser and thesecond detection laser to a sample tank (22); after reflecting the first detection laser and the second detection laser in the sample tank (22) for a plurality of times, emitting the laser out from alight outgoing opening (23) of the sample tank (22); then converging the laser into an absorption spectrograph (25) through an adjustable converging lens (24); transforming a received light signal into an electric signal through the spectrograph (25) and transmitting the electric signal to a computer (26); analyzing and calculating by the computer (26) to obtain a measured value N1 of the first detection laser and a measured value N2 of the second detection laser, and acquiring an accurate gas concentration value N. According to the method provided by the invention, double wavelengths are usedfor measuring and are mutually used as reference standards to carry out pulse width correction, and an accurate measurement result is obtained; the detection of the various gases under high precisionis met.