The local reaction induced in the track for low-density polyethylene irradiated with ion-beam was investigated. The transformations of the chemical structure induced by irradiation are on trans-vinylene, end-vinyl, vinylidine and the cross-link. The different reaction processes are induced in the micro-region of the track. These processes depend on the stopping power. In the region of larger stopping power, the rate of the process, which produces the end-vinyl, increases and that of the trans-vinylene decreases. These results suggest that the main chain scission of the polyethylene can be induced by very large energy deposition in the micro-region.