The invention relates to a building construction method, and discloses a construction method for releasing strong welded connection restraint stress of steel connecting rods on upper parts of two stiffened concrete structures which are oblique relatively. The construction method comprises the following steps: A, carrying out concrete pouring on floors and beams of the nth storey in one building; correspondingly setting after-cast section areas on which concrete pouring does not be carried out temporarily, at a place, which is required to be connected with a steel connecting rod, on nth storey in the other building, and constructing concrete pouring on the remaining floors and beams thereof; B, carrying out installation of steel connecting rods between nth floors of two oblique and stiffened concrete structures; and C, carrying out concrete pouring in the after-cast areas on the nth storey of the oblique and stiffened concrete structure of the other building after finishing installation of the steel connecting rods, completely cooling and fully releasing strong restrain stress. By adopting the construction technology of reasonably presetting the after-cast section areas, the invention enables the strong restrain stress generated by the steel connecting rods to be released successfully, enables the construction to meet structure design requirements, simultaneously, accelerates construction speed and achieves obvious economic benefits and social benefits.