The plants under different environmental conditions showed the differentiation of morphological traits and trade-offs and adjustment of material allocation. A comparative study was performed on morphological traits and allometric relationships of biomass allocation of reproductive and vegetative ramets of Phragmites australis in different habitats in Zhalong wetland using a large samples' survey and statistical analysis. The results showed that the growth of ramets of P. australis had great ecological plasticity in the saline-alkali habitats, xeric habitats, wet habitats and aquatic habitats at the end of September. The height and weight of ramets of P. australis in the four habitats were the largest in the aquatic habitat and the smallest in the saline-alkali habitat. The ratio of maximum values and minimum values of height and weight of ramets within the habitat were 1.3-3.3 and 1.8-5.1, while the variation of reproductive ramet was lower than that of vegetative ramet. The ratio of supportive allocation and productive allocation of ramets was 1.8-4.2. The productive allocation of ramet was the highest in saline-alkali habitat and the lowest in aquatic habitat, but supportive allocation and reproductive allocation were the opposite order to productive allocation. The relationship between length and weight of inflorescence and height of reproductive ramet was a linear function, and height and weight of ramet less than 20% and 35% of the population average could not have sexual reproduction. The relationship between leaf weight, leaf sheath and stem weight, and ramet weight and ramet height was a power function allometric scaling relationship. Plants adapt to the different environment by changing morphological traits and adjusting the material distribution among modules, and the growth relationship among modules controlled by genetic factors was relatively stable.