ε-HNIW was heated at 70 ℃,80 ℃,90 ℃ or boiling points in five solvents ( water,toluene,n-butyl ether,cyclohexane and heptane) for 240 min, respectively. The FTIR spectra of specimens sampling at different times indicate that polymorph transformation of ε-HNIW is related to dipole moment of solvents. When ε-HNIW was heated at the above temperatures for 240 min in solvents with dipole moments (water, toluene and n-butyl ether), the polymorph transformation took place,while in those with zero dipole moment (cyclohexane and heptane) under the same conditions, no polymorph transformation occured.