The utility model discloses a combined tower crane foundation structure which comprises a profile steel platform fixed on a building structure girder and a tower crane underframe fixed on the profile steel platform. The profile steel platform comprises six first girders, six second girders and six round steel pipe columns. Four first steel girders are arranged longitudinally, two first girders are arranged laterally, four second girders are arranged longitudinally, and two second girders are arranged laterally. Four supporting bases are arranged at the connection positions of the two lateral first girders and the two lateral second girders, connection boards are welded on the four supporting bases, a plurality of bolt holes are formed in the connection boards, and high-strength bolts penetrate through the bolt holes of the connection boards so as to fixedly connect the tower crane underframe onto the connection boards. The combined tower crane foundation structure solves the problem that tower crane foundations cannot be installed inside buildings when the reverse building method of buildings is adopted, and is reliable in the foundation, small in the total settlement, fast in installation and saving in time and energy.