The influence of phosphorus slag used as mineral additive on properties of cementing material is studied in this article. The results show that, with the content of phosphorus slag increased, the water demand of cementing material increased; the setting time prolonged; the hydration heat decreased. Under the same content of phosphorus slag, with the specific surface area of phosphorus slag increased, the water demand of cementing material decreased; the setting time shortened; but the hydration heat increased. The strengths of cementing material at 7 and 28 dates all decrease with the increase of phosphorus slag. At 90 dates, the change of strength with content of phosphorus slag is very small. The specific surface of phosphorus slag area mainly effects the early strength of cement stone.