Provided is a biomass gas generating and direct burning system. The biomass gas generating and direct burning system comprises a negative-pressure open type biomass carbonization device and a biomass gas direct burning device. The negative-pressure open type biomass carbonization device comprises a furnace body with a carbonization chamber at the top. The top end of the carbonization chamber is open, and the bottom of the carbonization chamber is provided with a fire grate. A gap communicating with a gas outlet in the top of the furnace body is formed between the side wall of the carbonization chamber and the furnace body. The gas outlet is connected with a negative pressure fan through a pipeline. The biomass gas direct burning device comprises a first burning chamber and a second burning chamber, wherein the front end of the first burning chamber is connected with an air inlet pipeline, the rear end of the first burning chamber communicates with the second burning chamber through a high-temperature hot airflow communication opening, the outer side of the first burning chamber is provided with a primary air distribution pipeline used for distributing air for the air inlet pipeline and a secondary air distribution pipeline used for distributing air for the rear end of the first burning chamber, and the first burning chamber is provided with an igniter. An outlet of the negative pressure fan is connected with the air inlet pipeline through a pipeline. The biomass gas generating and direct burning system can make generated high-temperature biomass gas be directly burnt for use, thereby being safer and more environmentally friendly.