The effects of toroidal rotation on tearing modes are studied. It is found that rotation affects the stability of tearing modes mainly through interaction with the resistive inner region of the tearing mode. The coupling of magnetic curvature with the centrifugal and Coriolis forces provides a perturbed perpendicular current, and a return parallel current is induced to affect the stability of tearing modes. Toroidal rotation plays a stable role, which depends on the magnitude of the Mach number and adiabatic index , and is independent of the direction of toroidal rotation. For , the scaling of the growth rate is changed for typical Mach numbers in present tokamaks. For , the scaling remains unchanged, and the effect of toroidal rotation is much less significant compared with that for .