Free electron laser (FEL) have been developed as tunable lasers over a wide range of wavelenths. Equipment in the region of 6-16 microns (1,660-630 cm-1) is available in the Beijing free electron laser erected by Institute of High Energy Physics, CAS. In this study we report first measurements of infrared-induced molecular change under irradiation by FEL of 9.414 microns and 6.228 microns, respectively. Taking o-amino-benzoic acid as an example, FTIR characterization indicates that the peak positions of both N-H and C=O stretching vibrations shift before and after the irradiation of FEL. It demonstrates that FEL induces the re-arrangement of H-bonds between COOH and NH2 by stimulating the vibration of carboxyl groups. It suggests that the presence of stable/metastable phases in the title compound.