The invention discloses a fixing device for preventing flotation of reinforcing steel bars in reinforced concrete. The fixing device comprises a template, a stainless steel sleeve and a T-shaped bolt; an internal thread hole is formed in the bottom of the stainless steel sleeve; the T-shaped bolt is inserted into the internal thread hole from the bottom of the template and fixes the stainless steel sleeve onto the template; one or more brackets used for bearing the reinforcing steel bars is arranged on the lateral side of the stainless steel sleeve in an outward extending mode; the brackets are provided with bending parts matched with the brackets to be used for fixing the positions of the reinforcing steel bars; a threaded rod and a nut are arranged at the upper end of the stainless steel sleeve; an inner template filling body sequentially comprises a filling main body, an upper cover and a pressing plate from bottom to top; and the threaded rod sequentially penetrates through the filling main body, the upper cover and the pressing plate and is connected with the nut. The fixing device can guarantee the thickness of upper and lower reinforcing steel bar protection layers of the concrete structure, guarantees the fact that the reinforcing steel bars over and under an inner template are sufficiently protected, and is convenient to use.