Method for fast measurement of methane content in biogas through indirect volume

The invention discloses a method adopting the indirect volume to quickly measure the methane content in marsh gas. The methane gas in the marsh gas is injected into a methane collecting bottle filled with work liquid; the work liquid of the same volume is discharged into a receiving bottle from the methane collecting bottle; and then the volume of the work liquid in the receiving bottle is measured so as to get the content of the methane in the marsh gas. The invention also discloses a methane quick analyzing instrument formed as follows: an outlet valve of a ZS-2 type marsh-gas content analyzing instrument is connected through a rubber tube with a methane collecting bottle; two apertures are arranged on the bottle cap of the methane collecting bottle for respectively arranging an intake tube and a discharging tube which is connected with a burette through a rubber tube; and the receiving bottle is arranged under the burette. The instrument is provided with a small volume; the measurement speed is high; the a