Laboratory triaxial tests are carried out to study the stress-strain relationship and strength property of coir fibre-reinforced soil. The reinforcement effect and the change rule in different reinforced cases is investigated. The experimental results showed that: mixing coir fibre in the red clay can improve the ability of deformation resistance. Only when the strain is big enough can the reinforced effect of coir fibre shows, and stronger effect at the bigger axial strain with the increase of triaxial strain. The stress-strain curve of coir fibre-reinforced soil is similar to a hyperbola, whose main damage mode is shown as ballooning destruction. It was shown that not only the cohesion but also the internal friction angle are improved when mixing coir fibre in the red clay. And the cohesion increases obviously, but the internal friction angle increases less. The reinforcement effect of coir fibre-reinforced soil improves gradually with the increase of dosage in the same conditions. The reinforcement effect of coir fibre-reinforced soil turns better with the lower confining pressure in the same conditions.