Abstract: This paper studies the effects and mechanical properties of soil reinforced with coconut fiber and double polyethylene polymer. The examined factors include the content of coconut fiber, the length of coconut fiber, and the content of double polyethylene material. They can influence stabilized soil mechanical properties and permeability. We use the orthogonal experiment method to conduct unconfined compressive strength tests and permeability tests by adding coconut fiber and double polyethylene polymer. Test results show that:the unconfined compressive strength improves and the permeability decreases after coconut fiber and double polyethylene material are added into the soil. Compared with the obvious impact of coconut fiber length on the unconfined compressive strength, coconut fiber content and double polyethylene material content have significant impact. Though coconut fiber length has no significant impact on the permeability coefficient, the influence of coconut fiber content and double polyethylene material content is clear. When fiber contents come to 0.9% and double polyethylene material contents reach 0.375%, the soil sample is of the largest unconfined compressive strength. When fiber contents arrive 0.9%, and double polyethylene material content 0.325%, the minimum permeability coefficient is observed.