Decisional impulsivity is one of the risk factors for occurrence and development of many mental disorders, and that the dysfunctions of orbitofrontal cortex (OFC) and nucleus accumbens core (NAcC) are at least involved. Although previous studies have shown that the role of OFC as a whole in regulating decision-making impulse behavior is inconsistent, it’s still unclear that the roles of the subregions of OFC including their projections to the NAcC in decisional impulsivity. The present study was designed to investigate the roles of OFC subregions, medial OFC (mOFC) and lateral OFC (lOFC) and their projections to the NAcC in decisional impulsivity in free-moving rats. We found that rats with low level of decisional impulsivity (LI) showed higher neuronal activity in both the mOFC and lOFC, and more neurons in mOFC but not lOFC projecting to the NAcC were activated, compared with high level of decisional impulsivity (HI) rats. The mOFC-NAcC projections of LI rats showed stronger information communication in beta and low gamma oscillations in the expected reward choice and delay time windows. Further, specific activation (in HI rats) or inhibition (in LI rats) of the mOFC-NAcC pathway could partly reverse their decisional impulsive behaviors. The findings first demonstrated that the mOFC-NAcC pathway was more important than the lOFC-NAcC pathway to the top-down control in decisional impulsivity, which could be a new neural physiological mechanism for psychiatric disorders associated with decisional impulsivity.