Abstract: Cystolith hair of papermul berry (Broussonetia papyrifera) grown on the yong stems, buds and leaves was a longish conical cell. The base of the hair was surrounded by funnel-form basis, and annular cystolith were situated on the base. As soon as the third young leaf of the bud grew, cystolith hair appeared. The hair was formed from large proepidermal cell which was formed by anisoanticlinaly livision. The basis of hair was formed by anticlinal and crossdivision of the proepidermal cells. The hair cell was formed on the tip 8 the hair cell from the lateral cell wall of the hair cell was formed only when the leaf reached 6cm in lengh and 4 to 5cra in width. CaSO4 was one of the components in cystolith. This is because cystolith could accumulate large amount SO2 and therefore is highly resistant to SO2 pollution. The result is a useful indicator for measurment and breeding of resistant plants for SO2 pollution. And this paper contributed diraction on physiological and biochemical mechanism research on the uptake of SO2.