The invention discloses a staggered mounting method of a lower furnace shell and in-furnace equipment of an air heating furnace, and belongs to the technical field of air heating furnace equipment mounting. The process of the method comprises the steps that a, a furnace shell bottom plate is mounted on a base; b, a first belt furnace shell is hoisted and is placed on the furnace shell bottom plate; c, the longitudinal and transverse center line of a grate is released on the furnace shell bottom plate, and marks are made on the first belt furnace shell and the furnace shell bottom plate; d, according to the marks, furnace bottom I steel and supporting columns are mounted; and e, the grate is mounted on the supporting columns, meanwhile, a second belt furnace shell is hoisted in place, and the first belt furnace shell and the furnace shell bottom plate are welded. By means of the whole mounting operation process, staggered mounting of the furnace shell and the equipment is achieved, andthe construction period is effectively shortened on the premise of guaranteeing the mounting precision of the equipment.