Diamond anvil cells combined with Raman spectroscopy and angle-dispersive x-ray diffraction (ADXRD) were used to investigate the compression behavior of cinchomeronic acid (C7H5NO4, CA), a hydrogen-bonded polymorphs. The compression of form-Ⅰ at approximately 6.5 GPa caused an irreversible phase transition that produced the new polymorph form-Ⅲ. Lattice and inteal modes in the Raman spectra were analyzed to determine the modifications in the local envi-ronment of CA form-Ⅰ molecules. The form-Ⅲ was indexed and refined to a low-symmetry triclinic structure with space group P1. The mechanism for the phase transition involved the reconstructions in the hydrogen-bonded networks in CA form-Ⅰ.