Past researches have been showed that about 50% of whole needed energy for different stages of agricultural production is used for tillage operations. One of the most important stages of tillage operation is breaking hardpans created naturally or by trafficking. Great amount of energy needed for braking hardpan using traditional sub-soiler. The objective of this research was to find a method to loosen hardpan using less enery with optimum tillage conditions. Most of researches have been shown using oscillatory sub-soiler (oscillation can be in horizontal, vertical directions or combination of both of them) can decrease required draft and incerase sub-soiler performance and its efficiency. The most important factors affecting the sub-soiler's performance are: oscillating amplitude, frequency, oscillation angle of tine also tractor forward velocity. In this study an oscillating sub-soiler was simulated using ADAMS software. Increasing frequency reduced the engagement time of tine with uncut soil. Draft was reduced with increasing frequency 69% draft reduction was obtained at 8.85Hz, compared with rigid tillage. The required engine power shows there is an optimum frequency close to 3.5 Hz for minimum power to operated the sub-soiler.