A total of 36 Xianan cattle aged 13-15 months and weighed (332.8±49.9) kg with similar genetic background were selected and randomly divided into 4 groups with 3 replicates in each group. Cattles in 4 groups were fed diets with phosphorus mass fractions of 0.15%, 0.18%, 0.20% and 0.23%, respectively, for a pretrial period of 15 days and a trial period of 60 days, to determine the growth performance of the Xianan cattle and the serum biochemical indicators, and to analyze the effects of dietary phosphorus levels on the rumen microbiota. The experiment results showed that dry matter intake in the 0.15% group was extremely significantly lower than that of the other three groups; average daily gain of the 0.18% and 0.20% groups was significantly higher than that of the 0.15% group, and the average daily gain of Xianan cattle was the highest, up to 0.92 kg at a phosphorus level of 0.20%. There was no significant difference in the apparent digestibility of dry matter, neutral detergent fiber, acidic detergent fiber, crude protein, and calcium among the groups of Xianan cattle, and the apparent digestibility of phosphorus increased linearly with increasing dietary phosphorus levels. Dietary phosphorus levels did not affect the concentrations of serum calcium, phosphorus, urea nitrogen, or the activity of alkaline phosphatase. There were no significant effects of dietary phosphorus levels on ruminal fermentation parameters in Xianan cattle. Bacteroidetes, Proteobacteria and Firmicutes remained the dominant phyla in the rumen. In conclusion, the recommended dietary phosphorus level for 13- to15-month-old Xianan cattle with a body mass of (332.8±49.9) kg is 0.20%.