Abstract: The harmful algal blooms(HABs)continually occurred in Dianchi Lake in recent years, and the harmful microcystis aeruginosa is the dominant species. In the project on the control of HABs in Dianchi Lake, gathering the microcystis with machine is now used on a large scale. The bloom of Microcystis has high protein content and a big amount of biomass, and it can be used as the raw material of fertilizer in the agricultural production. Since microcystins produced by Microcystis are very difficult to degrade, the utilization of the raw materials is restricted. Furthermore, if the removal or degradation of microcystins can’t be carried out in time, the possible risk of microcystins to environment will inevitable. Thus the detoxication and safe treatment of microcystis powder is necessary. In order to detoxicate the algal powder of Microcystis harvested from Dianchi Lake, three methods, the pH value adjustment, NaClO treatment and O3 treatment, were applied to deal with the algal powder. We measured the effect of detoxification and the loss of protein after the treatments. The result showed that the former two methods(the pH value adjustment and NaClO treatment) didn’t work well. With pH adjustment, the detoxication rate of the algal powder was 50%-66%, while it was 77% when NaClO treatment was used. The disadvantage of this method is that the application of a big amount of chemicals will cause environmental pollution. However, when 150mg/g of O3 was applied for per gram of dry algal powder, we found that it can detoxificate the algal powder in a short time and have a good effect. So, this method has a good prospect in practice.