The effect of the Rs-5 bacteria strain, identified as Klebsiella oxytoca and isolated with ACC as the sole nitrogen source, on salt stressed cotton seedling growth was studied. It was demonstrated that Rs-5 could obviously relieve salt stress and promote cotton seedling growth. After treatment with Rs-5, the individual plant height and dry weight of cotton increased by 14.9 and 26.9%, respectively, compared to the control. Further analysis found that Rs-5 exhibited the ability to increase the cotton’s absorption of the N, P, K, and Ca elements and decrease the absorbability of the Na element under salt stress. In addition, Rs-5 itself could produce phytohormone-auxin, and was capable of dissolving phosphorus (P). The ratio of the dissolved P diameter to the colony diameter was 1.86. The dissolved P was 81.6 mg·l−1 in media after four days of incubation.