The medicinal plants are well known traditionally as therapeutic agents, this study was aiming to prove the presence or absence of antispasmodic activity against intestinal spasm in some well-known medicinal plants. This activity was tested in vitro by induction of contraction of intestinal smooth muscles using acetylcholine and then inhibition of that contraction by the tested agents. The induction of contraction of smooth muscles and its inhibition by the tested agents was recorded on a graph as mechanical activity using the grass polygraph and compared to a control graph where atropine was used to inhibit the action of acetylcholine. This test was accomplished by using the organ bath, which contains a piece of intestine isolated from the rat. The study was done by using 50 rats of both sexes. This part of the study proved that only 3 agents out of 14 agents used in the study, have the antispasmodic activity. These are; Cinnamon, Olibanum, and Thyme. The second part of the study was done in vivo to confirm the results of the first part in relieving the intestinal spasm and induced by acetylcholine and determining the effect of the three effective agents on the serum levels of some electrolytes (Ca2+, Mg2+, Na+, and K+). This was accomplished by measuring the serum levels of these electrolytes by using atomic absorption, in normal condition of intestinal relaxation, and after the intestinal contraction was induced by acetylcholine, and after inhibition of contraction by administration of the three effective agents. Each agent was tested apart from the other two agents and on specific group of rats (10 rats). And to get precise results, the collected data were analyzed statistically by using t-test at (P <0.01). The results for the three agents were significant for Ca2+, Na+, and K+ and not significant for Mg2+, which are expected for the normal contractile process of the smooth muscle fibers of the intestine.