Knockout reaction of the exotic nucleus 8He from Hydrogen target at 82.3 MeV/nucleon were carried out at RIBF in RIEKN.The valence nucleon knockout mechanism and the core fragment knockout mechanism are discriminated through the detection of recoiled protons in coincidence with the fragments emitted at forward angles.This would provide a new method to directly probe the cluster structure of the projectile at its ground state.In addition in the case of valence nucleon knockout the reconstruction of the resonant state of the projectile could be performed without contaminations resulted from the core knockout reaction mechanism.Comparisons are made for measurements with or without recoiled proton tagging.