Objective To study the activity of protease-activated receptor 2（ PAR-2） in the physiological mechanism of lung being related to large intestine theory. Methods Totally 30 SD rats were randomly assigned to control group

pulmonary physiological activation（ PPA） group

colon physiological activation（ CPA） group

10 rats in each. The PPA group inhaled PAR-2 activator

1% trans-cinnamoyl-Leu-Ile-Gly-Arg-Leu-Orn- [amide ]（ tcLIGRLO） solution to make PPA rat models; the CPA group were used 1% tc-LIGRLO solution by colon administration to make CPA rat models. The pulmonary and colon functions

firing activity of vagus nerve

muscular tension and contraction frequency of the bronchus and colonic smooth muscle were observed. Results The carbon particle propelling rate

muscular tension and contraction frequency of the colonic smooth muscle in the PPA group was significantly higher than the control group

while the firing activity of vagus nerve reduced 10 min after activation（ P <0. 05）. The airway resistance and lung dynamic compliance of the CPA group was better than the control group

with the muscular tension and contraction frequency of the bronchial smooth muscle declining and the firing activity of vagus nerve ascending 10 min and 15 min after activation（ P < 0. 05）. Conclusion By stimulating PAR-2 on the bronchus or colon

the function of organs related to one another could be improved

which indicated that PAR-2 may act by regulating qi movements of the lung and large intestines in the physiological mechanisms of lung being related to large intestine theory.