Objective: To observe the changes of myoelectric activity and pressure in sphincter function of Oddi (SO) after short-term partial bile duct obstruction in guinea pigs. Methods: Sixteen English short-hair guinea pigs were equally randomized into sham operation group and model group, and underwent sham operation and establishment of partial obstruction of the common bile duct (CBD) respectively, during which, the CBD diameters were measured. At one week after operation, the CBD diameters were measured again, and the liver function parameters, as well as the electrical activity and dynamic variables of SO were determined. Results: After operation, the CBD diameter in sham operation group showed no significant change (P>0.05), but it was significantly enlarged in model group (P<0.05). In model group compared with sham operation group, the serum levels of bilirubin and liver enzymes were significantly increased (all P<0.05); the voltage amplitudes of both rapid and slow waves of SO were significantly decreased (both P<0.05), while the frequencies of them had no significant difference (both P>0.05); the basal SO pressure was increased but peak SO pressure was decreased significantly (both P<0.05), while the SO contraction frequency showed no obvious difference (P>0.05). Conclusion: Partial CBD obstruction can cause decrease of voltage amplitudes of rapid and slow waves, basal pressure increase and peak pressure decrease in SO, and these changes may be one of the important mechanisms responsible for being prone to acute biliary pancreatitis in partial CBD obstruction.