The invention discloses a modular fireproof inner partitioning wall to solve the problem that an existing inner partitioning wall is poor in fire resistance due to the fact that filling materials of the inner partitioning wall is inflammable, and belongs to the technical field of fireproof inner partitioning walls. The modular fireproof inner partitioning wall comprises a wall body, an inflaming retarding layer and a supporting steel plate. The wall body comprises an upper mold and a lower mold. A plurality of inner protrusions horizontally arranged are uniformed arranged on the lower portionof the upper mold. Inflaming retarding yarn filling grooves are formed in the inner protrusions. The fire resistance and the inflaming retarding function can be achieved by the inflaming retarding layer. Water vapour in the wall body can be quickly discharged by the inflaming retarding yarn filling grooves, and therefore mildew in the wall body can be avoided. Aramid fiber is breathable flame retardant fabric, and the inflaming effect is effectively achieved. Two adjacent wall bodies are fixed by a buckling assembly, stability of the wall bodies can be guaranteed, and excessive drilling and polishing in the construction process can be reduced meanwhile.