The efficient lasing output from 2 (2′ hydroxyphenyl)benzoxazole(HBO) in cyclohaxane, based on excited state intramolecular proton transfer (ESIPT), is reported. The laser energy conversion efficiency is measured to be about 17%. And the tuning range is 495 nm￣540 nm. By considering the mechanism of ESIPT, we develop a kinetic model of proton transfer laser for HBO to calculate numerically the spectra and instantaneous features of the broad band and narrow band emissions. The calculated results are in agreement with the experiment very well. In addition, the calculated results show that the pulse duration of proton-transfer laser dependents on the ground-state lifetime of keto-tautomer of ESIPT molecule.