Limestone powder is a readily available and inexpensive material. As an admixture, limestone powder partially replacing fly ash or slag which gets serious to supply today has great significance in the aspects of solving raw materials of concrete, reducing project cost and environment protection. Effects of complex adding of ultra-fine limestone powder and fly ash on the workability and strength of concrete are studied in this paper. Experimental results show that: The fluidity of fresh concrete increases with the ratio of ultra-fine LP to fly ash increasing. The slump loss decreases with the ratio of ultra-fine LP to fly ash increasing. When the ratio of LP to fly ash increases from 5:5 to 9:1, the W/B decreases slightly and the slump of concrete almost is in the region of 210-230mm, the compressive strength of concrete remain basically unchanged. The concrete can produce lots of air bubble when the ratio of ultra-fine LP to fly ash exceeds 8:2 .When the proportion of admixtures of ultra LP and fly ash exceeds 50%, the 28 days compressive strength decreases obviously.