This study investigates the scale effect on nonlinear behavior of a clamped-clamped circular graphene sheet nanoplate actuator, which is electrostatically actuated by various vdW forces, tensile loads, and hydrostatic pressures. The circular nanoplate model is developed by using Eringen's nonlocal elasticity theory. The nonlinear behavior of the circular nanoplate actuator subject to nonlocal effect, electrostatic vdW forces, tensile loads, and hydrostatic pressures, is then carefully derived, analyzed and presented. A proposed hybrid differential transformation/finite difference method is first introduced to characterize the influence of scale effect on nonlinear behavior of the circular nanoplate subject to DC loads. The modeling result shows that the pull-in voltage deviates less than 2.71% as compared to that appeared in the literature obtained by using a different approach. The validity of the proposed hybrid method is thus verified and can thus be employed to further characterize the effect of small scale for different electrostatic actuation of tensile loads and hydrostatic pressures in greater details. The structural modeling results indicate that the pull-in voltage increases obviously with increasing scale effects. Overall, the results also reveal that the hybrid method presented in this paper is effective and can be used to accurately quantify the pull-in voltage in circular nanoplate systems under different associated actuation.