We demonstrate a direct,fluorescence-free measurement of the oscillation frequency of cold atoms in an optical dipole trap based on a high-finesse optical cavity strongly coupled to atoms.The parametric heating spectra of the trapped atoms are obtained by recording the transmitted photons from the cavity with the trap depth is modulated by different frequency.Moreover,in our method the oscillation can be observed directly in the time scale.Being compared to the conventional fluorescence-dependent method,our approach avoids uncertainties associated with the illuminating light and auxiliary imaging optics.This method has the potential application of determining the motion of atoms with stored quantum bits or degenerate gases without destroying them.