Abstract: Test of potted plant and measurement absorbency were used to study physiological response of protein, reducing sugar and solution sugar of slash pine’s half-sib under water stress. There are 7 families comparison with general slash pine (ab. CK). The contents of protein, reducing sugar and solution sugar 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 indicated that either water grads or families of contents of protein, reducing sugar and solution sugar were notable difference. The protein content of slash pine’s families was first up and then down with increasing of water stress. The protein went up on the primary water stress and then down with linear on the medium and anaphase water stress. The reducing sugar and solution sugar were up with linear while increasing of water stress. The families of 1027,101,464 had more contents of solution sugar and ability of resistant drought was more. This is one of physiological cause of 1027,101,464 on fast growing and high yield.