A method of He-assisted fusion splicing is demonstrated to prepare the all-fiber hollow-core photonic crystal fiber (HC-PCF) low-pressure gas cell.In the preparing process,the high gas purity is guaranteed by flushing the HC-PCF with the high-pressure desired gas;the dynamical gas flow in the HC-PCF is studied with a self-made real-time spectral detection system;and a 10 m all-fiber HC-PCF low-pressure CO2 gas cell with the pressure of 70 kPa and insertion loss less than 2 dB is successfully prepared by He-assisted fusion splicing technique.This method may also be suitable for the fabrication of HC-PCF gas cell with lower pressure,and the prepared gas cell shows good air-tightness and long-term stability.