Abstract: Applied with test of potted plant and measurement absorbency for study physiological response of activity of cell defense enzymes and lipid peroxidation of slash pine’s half-sib under water stress. There are 7 families comparison with general slash pine(ab. CK). The contents of superoxide dismutase(SOD), catalase (CAT), antioxidant (AsA), malondialdehyde (MDA) and the rate of superoxide anion(-O2) generating are mensurated under normal water condition while soil water content is 70% and light water stress while soil water content is 55% to 60% and medium water stress while soil water content is 35% to 40% and heavy water stress while soil water content is 20% to 25%. The test result indicate that either water grads or families of contents of SOD,CAT,AsA,MDA are mighty notable difference. The rate of -O2 generating is notable difference within families. The rate of -O2 generating is mighty notable difference within water grades. The activity of SOD and content of MDA are up with increasing of water stress. The relationship of SOD, MDA and content of soil water is linear. The activity of CAT, AsA increase slowly in primary phase of water stress. Opposite the CAT increase sharply in anaphase of water stress. The activity of AsA up obvious and has maximum in metaphase of water stress. Opposite activity of AsA decline sharply in anaphase of water stress. The rate of -O2 generating decline slowly in primary phase of water stress and continue decline sharply in metaphase of water stress and up slightly in anaphase, but the value of rate of -O2 generating in anaphase is lower than in primary in water stress. They can clean MDA and activity oxygen and other injurant. Escaping MDA and phase. The SOD, CAT, AsA in body of slash pine’s half-sib have function normal and accordantly activity oxygen accumulate mass and keep full unction of cell and escape disturbing to physiological metabolize of slash pine’s half-sib and keep them develop normal and escape them injure. The SOD,CAT,AsA,MDA and rate of -O2 generating are not obvious rule within slash pine’s half-sib and CK on water stress. There are not significant protecting dominance within slash pine’s half-sib on water stress.