The invention provides a device for preparing synthesis gas from
biomass, and belongs to the field of
biomass utilization. The device comprises a
pyrolysis chamber as well as a heat exchange chamber and a graded gasification chamber which are arranged outside the
pyrolysis chamber in a sleeving manner, a
biomass feed port and a volatile component outlet are formed in the top end of the
pyrolysis chamber, and a
solid product outlet is formed in the bottom end of the pyrolysis chamber; a synthesis gas outlet is formed in the upper part of the heat exchange chamber, and the lower part of the heat exchange chamber is connected with the grading gasification chamber through a gas-
solid separator; the two sides of the grading gasification chamber are connected with a gas mixer, meanwhile, a tangential air
distributor is arranged below the grading gasification chamber, and the position where the gas mixer is connected with the grading gasification chamber is located above a
solid product outlet, so that the grading gasification chamber is divided into a reforming area and a preliminary gasification area. According to the invention, baking pyrolysis, graded gasification and
waste heat utilization are realized through three relatively independent spaces, the continuity of an object and the stability of a reaction are ensured,
reaction conditions such as
atmosphere and temperature are conveniently and accurately controlled, and a preparation process of clean synthesis gas is simplified.