Traditional researches on the squeezing effect of optical field are based on Heisenberg′s uncertainty principle and use root mean square (RMS) deviation to measure the quantum fluctuation of optical field. However, RMS deviation only contains the second-order statistical moments of the density operator. Thus under many circumstances, RMS deviation cannot precisely measure the quantum fluctuation. In fact, Heisenberg′s uncertainty principle is a special case of entropy uncertainty relation, and entropy can be used to measure the quantum fluctuation of the quadrature components of the field. Based on entropy uncertainty relation, the concept of entropy squeezing has been formulated. Entropy squeezing of the optical field in two photon Jaynes-Cummings (J-C) model is discussed. By comparing, it is found that the entropy exponential δxf(t) is more sensitive to the squeezing effect of optical field than the RMS deviation Δxf(t), and is a high sensitive parameter to measure optical field.