A system for recovery of methane hydrate from the deep ocean floor has not been established. As one possible recovery system, a gas-lift system was investigated. Experiments were performed with a gas-lift system of 5m height and 100mm in diameter to determine the relationship between injected gas quantity and pumped water quantity. Vertical flow in the gas-lift pipe was calculated with a compressible one-dimensional two-fluid model to analyze flow in the recovery pipe of methane hydrate from the deep ocean foot. Basic equations were mass conservation equations and motion conservation equations of each phase, the relation of volume fractions and the state equation of the gas phase. The calculation showed that the power requirement of the gas-lift system is 0.5 to 4% of power generated from recovered methane gas, and that optimal gas injection depths exist. Thus, the gas-lift system can be economically effective the recovery of methane hydrate from the deep ocean floor.