The switch from diffusive combustion to premixed combustion in a modern gas turbine changes the combustor exit temperature profile to a more uniform one. This will directly affect the cooling of the first stage vane especially the endwall region. A typical endwall configuration with matched nondimensional parameters to the engine condition was investigated experimentally in this study. Two endwall cooling arrangements at four different coolant to mainstream mass flow ratios (MFR) were tested in a linear cascade. Detailed measurements of pressure distribution, heat transfer coefficient, adiabatic film cooling effectiveness, and overall effectiveness of the endwall were performed. The temperature-sensitive paint (TSP) and pressure-sensitive paint (PSP) were used to acquire these parameters. The conjugate heat transfer characteristic of endwall with film cooling and impingement cooling was discussed. Moreover, the influence of coolant mass flow rate on conjugate heat transfer of endwall was analyzed. One- and two-dimensional methods for overall effectiveness prediction based on experimental data for separate parameters and correlations were also studied.