Te invention discloses an anti-grout-leakage prefabricated type connecting structure for a steel structure building. The anti-grout-leakage prefabricated type connecting structure comprises a floor deck and a wall body; and a connecting support plate is arranged at the joint of the floor deck and the wall body, a steel bar truss is arranged in the connecting support plate and provided with an upper reinforcing steel string, lower reinforcing steel strings, abdominal reinforcing steel strings and a bottom film, the abdominal reinforcing steel strings are arranged on the bottom film, the upper reinforcing steel string is arranged between the two abdominal reinforcing steel strings, and the lower reinforcing steel strings are arranged on the lower portions of the abdominal reinforcing steel strings. According to the anti-grout-leakage prefabricated type connecting structure for the steel structure building, the connecting support plate is arranged at the joint of the floor deck and the wall body, the connecting support plate forms natural anti-grout-leakage filling, and a large connecting plate width can meet the requirement for gap filling caused by that the on-site cutting precision of a steel bar truss deck is low; the steel bar truss on the steel bar truss deck can achieve effective overlapping connection, construction requirements are met, and a knee-brace used for supporting the floor deck beside a column cannot be arranged; and the problems that grout leaking happens and exquisite prefabricating cannot be achieved caused by the site construction of the steel bar truss deck are solved effectively.