Some factors inflnencing the effect of the treatment of phosphor wastewater with chlorine dioxide was studied. The experimental results showed that chlorine dioxide could oxidize phosphor and cyanide in wastewater. Under proper reaction condition, the oxidation yield of phosphor was 100%,and the oxidation yield of cyanide was over 90%.The first standard in GB 4283-84 could be attained after wastewater was treated with chlorine dioxide and lime.