The invention discloses a landfill gas collecting, purifying and generating process, and the construction of a gas collection vertical shaft by the process comprises the following steps of: (1) forming a hole and built shaft by adopting the self weight of a grab bucket; (2) repeating the step (1) till the gas collection vertical shaft reaches to the preset depth; (3) installing shaft body pipelines and installing gas collection pipes on the shaft body pipelines above the ground; (4) installing a landfill leachate discharge pipes in the shaft body pipelines; (5) installing a dissolved gas water forming device; (6) presetting shaft top sealing plates of the water discharge pipes and plug-in holes of compression air pipes at a shaft top; and (7) connecting divisions of all the gas collection pipes of the gas collection vertical shaft of a landfill with a plurality of gas collection stations and arranging a valve on each of the gas collection pipes. Clean and stable gas sources are arranged for a generating station through the landfill gas collecting, purifying and generating process.