A blue-pigment producing Streptomyces isolated from soil was identified,the properties of the blue pigment were studied.The results showed that the blue pigment has no odor, and is well dissolved in water or methanol.The color of the pigment is red below pH 8 and blue above pH 8. It is relatively stable at 100 ℃ for a short time and under the lights including ultraviolet rays when the value of pH around 7. Metal ions such as Ba 2+ 、K + don't have any effect on the pigment stability. The concent ration of Fe 2+ make the pigment denatured above 5×10 -4 mol/l, a little effect below 5×10 -5 mol/l. Pb 2+ precipitate the pigment ,but the pigment redissolve after HCl-Ethanol was added.The pigment can be exploited as natural pigment or potential pH indicator.