Abstract: Lake Chenghai is located 1503m above sea level on Yun Gui Plateaus in China. It belongs to subtropics semidryness climate, annual average temperature is 19℃, rainfall averages about 740mm per year. Lake Chenghai is deeper with an average depth of 25.7m. The lake area is 77.2km². It's an alkaline lake, the water pH ranges from 8.6 to 9.3. The cultivation of Spirulina platensis in the water of Lake Chenghai has been studied under the climate conditions of Chenghai region. CH-1, CH-2 and CH-3 media have been got in this experiment. The outdoor culture lasted 240 days. The cultivation area is 75m². Dried algae was 12.5/m².d in 20 days. The purity is up to 95%. The protein contents ranged from 55% to 63% of the dry weight. Except TRP which has not been measured, it contained another 17 kinds of amino acids, From the population of Spirulina platensis which had been cultivated in the water of Lake Chenghai, a new strain, Spirulina platensis str. CH-1, was selected. To compare with eriginal strain, its algal filament and thread pitch are longer, and the helix is also wider. It has clear superiority of floating character. It suits to growth in the media that made up with alkalic water.Our experiment show that it is suitable to develop Spirulina production in Chenghai region.