The invention provides a biomass gasification system, comprising a gasification furnace and a feeding device, wherein the gasification furnace comprises a furnace body and a blanking pipeline; the furnace body comprises a gas outlet, a fire grate and a feed inlet; the gas outlet is formed in the sidewall of the furnace body; the fire grate is arranged on the bottom of the furnace body and is provided with a gas inlet; the blanking pipeline is arranged on the top of the furnace body at a position corresponding to the feed inlet; the feeding device comprises a storage bin, a feeing pipeline, a kicking mechanism, a first hermetic door, a second hermetic door and a sealing assembly; the feeing pipeline is arranged on the top of the storage bin; the first hermetic door is arranged on the feeing pipeline; the kicking mechanism is mounted on the bottom of the storage bin; the second hermetic door is arranged in correspondence with the blanking pipeline and is provided with a driving rod; the driving rod is provided with a sealing cover; the sealing cover comprises an upper end surface and a sidewall, and the upper end surface is provided with small holes; the sealing assembly comprises a water tank arranged on the storage bin; the water tank is provided with a channel used for penetrating the driving rod; the channel is tubular; and the sealing cover covers the channel. The biomass gasification system provided by the invention has good airtightness during feeding, and is uniform in feeding, safe and highly efficient.