OBJECTIVE： To study the analgesic effect and mechanism of Gutongtie paste on model rats with formaldehyde-induced pain. METHODS： 60 SD rats were randomly divided into blank group， model group， Gutongtie paste low-dose， medium-dose， high-dose groups （0.594， 1.188. 2.376 g/paste， containing crude drug 0.48， 0.96， 1.92 g） and prednisone acetate group （ig， 0.005 4 g/kg， external bonding matrix）. Model rats with pain was induced by formaldehyde method and immediately administrated after modeling. Electronic tenderness instrument was adopted to determine the pain threshold of rats’ ankle joint after administration of 1， 2， 3， 4， 6 h. After 6 h， blood sample 0.3 mL was taken from abdominal aorta then rats were sacrificed. Enzyme linked immunosorbent assay （ELISA） was conducted to determine the β-endorphin （β-EP）， prostaglandin E2 （PGE2） contents； spectrophotometry was used to determine nitric oxide （NO） content in rats’ serum and inflammatory tissue； and radioimmunoassay was adopted to detect the substance P content in rats’ serum， inflammatory tissue and brain tissue. RESULTS： Compared with before modeling， pain thresholds in model group at each period were significantly decreased （P＜0.05 or P＜0.01）. Compared with blank group， PGE2， NO of rats， substance P content in inflammatory tissue and brain tissue in model group were significantly increased （P＜0.05 or P＜0.01）. Compared with model group， pain thresholds in Gutongtie paste groups at corresponding time points were increased， PGE2 and substance P contents in inflammatory tissue and brain tissue were decreased （P＜0.05 or P＜0.01）； β-EP and NO contents in serum in Gutongtie paste medium-dose， high-dose groups （P＜0.05 or P＜0.01）， NO contents in serum in Gutongtie paste high-dose group were decreased （P＜0.05）. CONCLUSIONS： Gutongtie paste has a certain analgesic and anti-inflammatory effect， and the mechanism may be related to reducing PGE2， NO， substance P contents， increasing β-EP content.