There is a significant diminution in the hydrostatic pressure coefficients (PCs) of the photoluminescence (PL) for InAs/GaAs quantum dots (QDs) in comparison wi th that of bulk binary. We study this phenomenon with the nonlinear elasticity t heory. The variation of the lattice and elastic constants plays an important rol e in the change of PCs, which causes the obvious decrease of the built-in strain s in InAs/GaAs QD. Therefore, the energy gap and the electronic confined energy change with pressure subsequently. It is the main reason for the measured small PCs of PL from QDs. Also the calculation reveals that the PCs are sensitive to t he sizes of QD. The smaller the quantum dot is, the more greatly the change of t he electronic confined energy affects the PCs. This effect gives rise to the inc rease of PCs when dot size is reduced.