Achromobacter spanius was endophytic bacteria cellulase producing . It was irradiated by gamma rays at doses from 0.5 – 5 kGy. The irradiated Achromobacter spanius increase extracellular cellulase enzyme activity over the non-irradiated strain. Irradiated strain at dose 3.5 kGy was identified as higher cellulase enzyme activity than those of other doses. Purification and characterization of cellulase produced by irradiated Achromobacter spanius was done. The cellulase enzyme was purified by applying sephadex G-100 gel chromatography technique. The highest activity of cellulase was obtained at enzyme volume and incubation period 0.2 ml and 30 minutes respectively. The optimum pH value was 7 and the optimum activity with temperature was 35 oC. The enzyme showed the highest activity when carboxmethyl cellulose (CMC) used as substrate on reaction mixture. According to thermal stability, the purified cellulase has high activity after 5 minute when purified enzyme was incubated at 60 OC. The purified cellulase, with a molecular weight (M.W.) of 32.5 kDa,