The invention discloses a low-boiling-point fuel combustor. The low-boiling-point fuel combustor comprises a fuel injection pipe, a primary air chamber, a pre-mixing chamber, a mixer, a diffusion combustion chamber, a secondary air chamber and an igniter. The fuel injection pipe stretches in the middle-rear part of the pre-mixing chamber from the front end of the pre-mixing chamber, the tail end of the fuel injection pipe is open, and a conical non-return body is arranged at the tail end of the fuel injection pipe; the primary air chamber is formed in the front end of the pre-mixing chamber; the primary air chamber is formed around the fuel injection pipe; the flow section of the pre-mixing chamber is of a square structure, and the mixer is arranged between the pre-mixing chamber and the diffusion combustion chamber; the mixer is in extension connection with the diffusion combustion chamber; the diffusion combustion chamber is square, and the wall surface is a linear or corrugated-plate-shaped heat accumulator built from a refractory material; the secondary air chamber is formed around the diffusion combustion chamber; and the igniter is arranged on the extension connection section of the mixer and the diffusion combustion chamber. More than two groups of flow guide walls built from the refractory material are arranged in the diffusion combustion chamber from top to bottom, and the flow guide walls are linear or corrugated-plate-shaped. The low-boiling-point fuel combustor disclosed by the invention has the advantages of being good in air-fuel mixing effect, capable of realizing staged low-nitrogen combustion and large-space combustion, and the like.