This study intended to investigate the structure and growth of reed canary grass (Phalaris arundinacea) in mires with changing environmental and climatic factors. The main idea was to find out the effect of climate change in an energy grass (reed canary grass) in future. In this research, reed canary grass (RCG) growth was measured at normal condition and changed environmental condition (at higher concentration of CO2 and at higher temperature). Similarly, its growth was measured at different water level. Three different age groups of RCG were included in the treatment to see the effect of climate change on RCG age. Climate change produced mixed effect on different structural parameters of RCG. However, total biomass seems to be increased with increase in CO2 concentration and temperature with clear increment in belowground biomass. Based on this research, considerable increase in RCG growth and biomass can be predicted in future under increased CO2 concentration and higher temperature. This research is based on data from only three months. Long-term analysis is needed to quantify more precisely the degree of increment in RCG biomass.