Objective To study the influences of Rheum palmatum L. （administrated for a long time） and the interstitial Cajal cell （ICC） on colonic electromuscular in rats with spleen deficiency. Methods Fifty rats were randomly divided into the control group and the group administrated Rheum palmatum L. After 3 months the slow wave frequency and amplitude of colon were detected. The changes of ICC were observed by using ZIO method and the pathological changes of dynamic basic functional unit （DBFU

i.e. ENS-ICC-SMC） were observed with transmission electron microscope （TEM）. Results In rats with spleen deficiency induced by long-time administration of Rheum palmatum L. the slow wave frequency and amplitude of colon decreased. The electric rhythm of colon was abnormal. The coefficient of variation （CV） of slow wave frequency and abnormal rhythm index （ARI） increased obviously. The neurofibers of intermuscular neuroplexus were poor distributed

the connection was disorder and ICC was few in TEM vision. The vacuolar degeneration of intermusclar nervous axon and degeneration of ICC were observed by TEM. Conclusion The long-time administration of Rheum palmatum L. can induce the decrease of slow wave frequency in rats with spleen deficiency. The mechanism may be related to the pathological changes of DBFU.