文章应用基础公式，推导液压系统油压极值比与极值比效率之间的关系式。该式说明，油压极值比越大，极值比效率就越低。提出了油压极值比是可以设计和选择的。

This article applies basic formula to the calculation of a relationship between the hydraulic pressure extremes ratio of hydraulic system and the extremes ratio efficiencies. This relationship shows that the greater the hydraulic pressure extremes ratio is, the lower the extremes ratio efficiencies are. The article holds that the hydraulic pressure extremes ratio can be designed and chosen.