The invention relates to the field of assembly type steel structure buildings, in particular to a beam through mortise and tenon type node structure of an assembly type steel structure and an assembly method of the node structure, and the produced beam through mortise and tenon type node structure can be taken as the node applied in the assembly type steel structure building. The structure comprises through main beams, main beam upper flanges, main beam lower flanges, main beam webs, cut auxiliary beams, auxiliary beam upper flanges, lower beam lower flanges, auxiliary webs, auxiliary connection dowels, 1 / 4 mortise and tenon steel pipe columns, upper mortise and tenon grooves, lower mortise and tenon grooves, splicing partition plates, ordinary steel beams and ordinary steel pipe columns. According to the beam through mortise and tenon type node structure of the assembly type steel structure and the assembly method of the node structure, the main beams, the cut auxiliary beams and four 1 / 4 mortise and tenon steel pipe columns are connected. According to the structure and the assembly method, the building space is saved, the force transmission path is clearer and more reliable, the construction is simple and convenient, the actual engineering design and construction requirements are met, the welding workload is small, environment protection and energy saving are realized, and the current requirement for green buildings is better met.