A hybrid optomechanical system consisting of an optical parametric amplifier and Coulomb force was proposed to observe the double optomechanically induced transparency (OMIT) by introducing the Coulomb coupling between the two nanomechanical resonators. The tunable characteristics of OMIT were studied under the resolved sideband regime and red detuning. The tunable double-OMIT can be observed from the output field at the probe frequency by controlling the intensity of the Coulomb coupling. The distance between the two transparency windows is increased symmetrically by enhancing the intensity of the Coulomb coupling. Changing the delays of two nanomechanical resonators can only bring about a slight influence on the depth of the double windows. The double-OMIT windows will broaden out only by enhancing nonlinear gain of the Optical Parametric Amplifier (OPA). A narrower transparency windows than the case of empty cavity can be realized by phase matching when the phase of the field driving the OPA was considered. These results might be applied to light storage and precision measurement.