通过对石化产品市场价格分析，得出石化产品市场周期性表现为"长周期"、"短周期"交替出现，长周期时间跨度在12年左右，短周期时间跨度不超过7年。同时，原油价格与石化产品价格走势基本一致。预测石化行业下一个景气高点在2021—2023年，石化投资可据此安排装置建成投产时机，以期获取更好经济效益。

It is found that the periodicity of petrochemical products market is characterized by the alternation of "long cycle" and "short cycle" through analyzing market prices of petrochemical products.The time span of a long-cycle is around twelve years and that of a short-cycle is not more than seven years.Meanwhile,the trends of crude oil prices are similar basically with that of petrochemical products.It is predicted that next profits peak for the petrochemical industry will appear during the period of 2021 to 2023.Petrochemical investors are suggested to arrange startup of new projects according to this period,in order to gain utmost profits.