The aero-optical aberrated wavefronts are measured by applying Hartmann wavefront sensor when the collimated parallel beam passes through a low speed heated turbulent jet. Proper orthogonal decomposition (POD) and the low dimensional approximation are applied to the aberrated wavefront time series, the comparisons between the measured wavefronts and low dimensional approximation reconstruction wavefronts of 16# and 1008# were conducted. The results indicated that the aberrated wavefronts can be expanded by the POD group and can be described with a few POD modes, with the more the reconstruction modes the more the reconstruction precision. Due to the difference of the spacial correlation of phase pulsating quantity at different wavefront positions, the reconstruction precision different data points is not same for the same reconstruction modes.