The high price difference of PVC appears in April-May and August-September every year. At that time, the price was just in the upward stage, because April, especially April-May, coincided with the overhaul of large factories in Asia, the supply was tight, and orders gradually increased. Downstream enterprises generally accumulate a certain demand, but when the supply is less than the demand, the price will go up. September-10, the price will be in a stable stage. When it enters the high temperature from July to September, the operating rate will decrease. For example, the whole export orders in East China and South China markets have also started mass production, and the downstream demand will increase. At this stage, supply is less than demand, so the annual price peak appears in August and September. At the end of August last year, the price of 8900 or even 9200 yuan came out, and then it began to decrease. On September-10, the calcium carbide plant began to be overhauled, but because the demand began to decrease, especially on February-10/2, the construction-related industries began to stop working and the price went up. This is the law of PVC price for one year.