Relaxation time of the polymer solution from rod-climbing experiment is analyzed in this investigation. For a low deformation rate, the polymer solution can be regarded as a second-order fluid and rod-climbing constant for the second-order fluid is correlated with the rheological properties of that polymer solution. Climbing constant(3) of polymeric fluid is measured first and then from the correlation between rod-climbing constant and relaxation time of the polymer solution which we have obtained previously, the experimental relaxation time of PIB(polyisobutylene)-PB(polybutene)-kerosene system is obtained. In addition, by analyzing the molecular weight distribution of polymers, we also calculate the relaxation time based on the Muthukumar and Freed theory which. was derived by generalizing the effective medium theory of the hydrodynamics of a polymer solution. Relaxation times from the rod-climbing experiment are found to be well correlated with the theoretical relaxation times.