The variation of interchain potential in poly (vinylidene fluoride) polymer during chain rotation was calculated.In the case that center chain rotates while all other chains keep static as discussed by “six-site-potential” theory,the potential curves show four high potential barriers owing to the steric effect of fluorine atom from adjacent molecule,which is in contrast to the six-fold sysmmetry pre-dicted by the “six-site-potential” model.It was found that if all chains rotate synchronically, the barrier height will reduce dramatically.The result also indicates that the polarization reversal is ac-complished with the change of lattice constant.The finally obtained barrier height is about 7.5kJ/mol.In comparison with the thermal energy of chain rotation at room temperature (about2.5kJ/mol),the potential well is too shallow to form stable spontaneous polarization.It was specu-lated therefore,the formation of spontaneous polarization in these materials should include some ex-ternal factors.