Both pulmonate Radix swinhoei and prosobranch Bellamya aeruginosa are common freshwater snails in many Chinese lakes. Two outdoor experiments were conducted to investigate whether a mutualistic relationship exists between the two snail species and submerged plant Vallisneria spiralis. Results indicated that herbivorous snail R. swinhoei at low density stimulated V. spiralis growth through consuming and removing periphyton on plant leaves and the mutualistic relationship significantly existed between them, and as snail density were further increased, the evident herbivory of snails on live plant tissue suppressed the plant growth. For B. aeruginosa, the snails at experimental densities significantly stimulated plant V. spiralis growth, there is always a mutualistic relationship between them. This study suggests mutualistic relationships between freshwater snails and macrophytes depend on snail species.