A newly developed method for the measurement of extensional viscosity was introduced to in-vestigate the extensional behavior of pitch during melt spinning. The confidence of this method was confirmed with the 3.6% of tolerance limit. The theoretical equation based on the viscoelastic model to calculate the extensional viscosity was proposed and its results were compared with experimental data. The spinnabilily of the isotropic pitch would be depended more viscous rather than elastic effect sinces the extensional viscosity found was of pitch independent of drawing ratio. During the melt spinning of pitch, measured force was rhelogical force by the extension. Therefore, innertia, gravity, air drag force was negligible.