We have investigated the superconductivity of Ca2+-dopped Gd1-xCaxBa2Cu3O7-y compounds under both ambient and high pressure. Using a Bridgman-anvil cell, the high pressure up to 9.0GPa, in temperature range of 1-300K, have been obtained. The superconducting transition temperature Tc (onset) initially increases with pressure at a rate of dTc/dP=7.68, 7.8 and 4.46K/GPa for x=0.10, 0.15, 0.20 samples at 0GPac has been investigated. By using the data of the structural parameters of samples at ambient pressure and the changes of the distances between cation and oxygen with the pressure, the role of the CuO2 plane on superconductivity is demonstrated. The coupling between the CuO2 planes may be used to explain the nonlinear dependence of Tc(P).