We demonstrate systematic investigations of high-order-harmonic generation resulting from the interaction of hydrogen gases with localized surface plasmons. These plasmonic near-fields are produced when a bow-tie-shaped metal nanostructure is subject to an intense two-color laser pulse. By changing the relative phase and relative intensities, cut-off frequency will be controlled in high-order harmonic spectrum. The results show that the maximum cutoff frequency pulse can be observed by using a half-harmonic control pulse with a same relative strength and  phase shift relative to the fundamental pulse.