Electron paramagnetics resonance has been used to analyze the produced effects in the single crystals undoped of potassium dihidrogen phophate (KH2PO 4 or KDP) that were irradiated with electron’s beams of 6 M eV energy and they received dose of 1, 21, 36 y 51 Gy . We identified the paramagnetic center (PO3) 2- that they were labeled with a and b, which are stables a room tempature. The spectrum were taken to 300 oK with the magnetic field perpendicular to the c axes of the crystals. Finally the paramagnetic centers concentration was calculated as function of the provided dose.