Abstract: The molten polymer's entanglement networkis assumed to deform nonaffinely and the transient network structural theorywith the revised upper convected Maxwell constitutive equation is used toestablish a new nonaffine network structural model of molten highpolymer in a sinusoidal strain field. With the simplified initialcondition, we can easily carry out its numerical analysis.The predicted value agrees with the experimental value, and theprecision of the nonaffine network structural model is higher than thatof the affine network structural model.