This paper reports a new method for determining viscosity in polymer solutions by headspace gas chromatography. It is based on kinetically measuring the methanol released from the polymer solution at a given temperature. The results showed that the present method has a good precision (with the relative standard deviation <2.14%) and good accuracy (R-2 = 0.970) when compared with the reference method. The present method is suitable for efficiently determining the viscosity in polymer-related research and applications.