The response of leaf functional traits to the shift in environmental variables can raise plant adaptiveness in a wide variety of habitats and subsequently broaden their ecological niche. This study aims to determine the differences in leaf functional traits between simple and compound leaves of Canavalia maritime to illuminate the mechanisms underlying the ecological strategy of plant species with different leaf forms. Single-leaf wet weight of compound leaves of C. maritime was significantly lower than that of simple leaves of C. maritime. Thus, compound leaves of C. maritime possess higher resource capture ability as well as higher relative growth rate than simple leaves of C. maritime. The petiole length of compound leaves of C. maritime was significantly higher than that of simple leaves of C. maritime. Thus, the biomass allocation to petiole for compound leaves of C. maritime was significantly higher than that of simple leaves of C. maritime. Meanwhile, the higher range of phenotypic plasticity of SLA of compound leaves of C. maritima may enhance the advantage in resource (especially sunlight) capture and use efficiency by shifting the material investment per unit area and per lamina.