A method of using the shifts of the beam resonant frequencies to determine the unknown parameters of nonlocal effects together with other effects such as surface elasticity, surface stress and residual stress is presented. The nonlocal effects are size-dependent, which only stand out when a specimen size diminishes. However, when the size of a specimen is small, other effects may also impact its mechanical properties and it is difficult to tell them apart. Unlike the static tests, the dynamic method presented in this study can differentiate various effects and thus determine the parameters. The parameters of different effects are solved as an inverse problem and the accuracy of the method is also demonstrated. So far, there are still no clear physical mechanisms to determine the parameters of nonlocal effects and different experiments yield different results. Because of the sensitivity to pre-existing defects, the mechanical properties of a small specimen may vary from one to another and the nonlocal effects can be disguised by other effects, which leads to different or even wrong interpretations on experimental data. With the capability of differentiating various effects, this study provides a more accurate and reliable method of determining the parameters of nonlocal effects, which should be of some help to the nonlocal theories.