The extensional rheology of low density polyethylene (LDPE) is studied bymelt spinning technique. Melt spinning mastercurves for LDPE are plotted for the measurement results of various temperatures and extrusion velocities. Linear relations between scaling factor b and T, Logb and Logv0 have been found. The analysis indicates that b can be regarded as a useful index of combination effects on the pre-orientation before extension, and on the unwrapping and orientation of macromolecular chains during extension. By using the values of b and the data from reference curve, extension viscosity curves of any setting temperature and extrusion velocity can be calculated, which will effectively enlarge the measurement range of melt spinning technique.