A direct numerical simulation of single plume flow in thermal convection with polymers was carried out in a domain with 1:3 as the width to height ratio. The heat transport ability is weakened by adding polymers within the here-investigated governing parameter range. However, it is promoted when the maximum polymer extension L is increased. The distribution of vertical velocity and temperature indicates that the plume in the polymer solution case is speeded up and widens bigger as compared to that in the Newtonian fluid case. Inside the plume, polymer chains tend to release energy at the position where the velocity is decelerated. The ratio of Nusselt numbers (Nu/NuNew) shows the power-law scaling relation with the governing parameter L2/Wi in polymer solution cases, which is only applicable for moderate Wi and small L. The present study can give direct insight into the observation about plumes in turbulent thermal convection experiments. It is therefore useful for the analysis of heat transport in thermal convection with polymers.