It was showed in literatures that polymer fluids (as melts or solutions) which have similar viscosity but different elasticity, their theological and processing behaviors were widely divergent.The measure method and norm for fluid elasticity are not a circumstance to fluid viscosity. The physical quantities to describe of fluid elasticity in literatures were various [1-2] There are distinguished about three classes: 1) a class of elastic modulus, includes melts strength, extensional viscosity, inlet pressure drop, etc. 2) a class of resiliency, includes recoverable strain, die swell,compliance, pressure at die exit, exc. 3) the normal stress differences, they have scientific significance but are difficult to measure.
