Numerical simulations were performed to predict the film cooling effectiveness and heat transfer coefficient distributions on a rotating blade platform with stator-rotor purge flow and downstream discrete film-hole flows in a 1-12 turbine stage using a Reynolds stress turbulence model together with a nonequilibrium wall function. Simulations were carried out with sliding mesh for the rotor under three rotating speeds (2000 rpm, 2550 rpm, and 3000 rpm) to investigate the effects of rotation and stator-rotor interaction on the rotor blade-platform purge flow cooling and discrete-hole film cooling and heat transfer. The adiabatic film cooling effectiveness and heat transfer coefficients were calculated using the adiabatic wall temperatures with and without coolant to examine the true coolant protection excluding the effect of turbine work process. The stator-rotor interaction strongly impacts the purge slot film cooling and heat transfer at the platform leading portion while only slightly affects the downstream discrete-hole film cooling near the platform trailing portion. In addition, the effect of turbine work process on the film cooling effectiveness and the associated heat transfer coefficients have been reported.