Abstract: The cooling design of a 201.25 MHz, 750 keV radio frequency quadrupole injector is described in this paper. The essential parameters for the design of the cooling pipes are obtained from the RF structure design. The hydrodynamics and thermal characteristics are theoretically analyzed. Computer simulation is performed using the steady state thermal analysis module of the radio-frequency software. Numerical computation shows that the increase of temperature is controlled within 1 K, the accelerator can work steadily with this cooling system. The cooling design satisfies the physical requirement very well．