In an anaerobic/aerobic sequencing batch reactor (SBR), the effect of organic loading rate (OLR) on the formation and phosphorus removal efficiency of granular sludge was investigated under the condition of 1.0-2.0 mg/L of dissolved oxygen (DO) concentration in the period of aerobic feast time in an SBR-cycle. Experiment results showed that the sludge in the SBR was the mixture of a majority of activated sludge floc and a small quantity of round-shaped granular at the OLR of 0.482-0.986 kg/(m3 x d). Granulation was accelerated at the early time of the OLR of 2.218-2.263 kg/(m3 x d), while the morphology of granules changed to an irregular shape on the end of the OLR of 2.218-2.263 kg/(m x d). Then the OLR decreased to 1.113-1.182 kg/(m3 x d), the mature granules were cultivated successfully. The morphology of the mature granules was nearly spherical with a very clear outline. The dimension of granules was 1-2 mm, and the granular sludge had a good settle ability [sludge volume index (SVI) between 20-22 mL/g]. The OLR also had influence on efficiency of phosphorus removal, when the OLR was elevated to 2.218-2.263 kg/(m3 x d), the efficiency of phosphorus removal declined from 99% to 78%, and could not be recovered even if the OLR was decreased to 1.113-1.182 kg/(m3 x d).