Abstract: A field study was undertaken to investigate the growth and reproduction response of P. malaianus to water depth gradient. The results showed that the stem length of P. malaianus was decided by water depth where the plant grows. There is a significant relationship between stem:leave ratio of P. malaianus and water depth gradient. that the relationship between below-ground biomass of P. malaianus and water depth gradient was not found. With increasing of water depth, the number of plantlet and inflorescence gradually dwindles.