The invention provides a semi-open type coalbed methane nitrogen expansion liquefaction technique by adopting swing pressure to absorb the excess pressure, belonging to the chemical and low temperature technical field. The invention provides an adsorption-liquefaction integrated flow of the high nitrogen content coalbed methane. Before the liquefaction process, most part of the nitrogen in the coalbed methane is removed in the pressure-swing adsorption process; afterwards, the coalbed methane is liquefied by the nitrogen expansion and liquefaction process, wherein, the nitrogen with excess pressure separated by the adsorption process is mixed with certain amount of circulating nitrogen to form the semi-open type nitrogen expansion circulation, different mixing processes are designed according to different ranges of the absorbed excess pressure to provide refrigerating amount for the coalbed methane liquefaction, thereby saving the nitrogen compression work and lowering the liquefaction work of the unit product of the system. Moreover, the higher the nitrogen content in the raw material gas of the coalbed methane, the higher the adsorbed excess pressure and more power dissipation is saved.