Theileriosis is caused by an intracellular protozoan that causes great economical losses to animal husbandry in different regions of Iran . The present study was done in order to identify of Theileriaovis in hard ticks in Lorestanprovince . Amongst five different regions in Lorestan, and during the April-to-july period of the year 2012, 265 cases of hard ticks were collected from the ear and the body surface and 100 blood smears from ear veins of anemic and feverish sheep. DNA extraction was done from the salivary glands of collected ticks and PCR test was performed using a pair of 520 bp specific primer of SSurRNA gene of T. ovis . The microscopic examinations of blood smears showed that 12 samples of blood smears ( 12 %) contained the piroplasmic forms of Theileriaspcies. The PCR revealed that 37 out of 152 Rhipicephalussanguineus (24/34 % ) were positive for T. ovisgenum including 21 female (13/81%) and 16 male (10/52%) ticks while the other ticks were not infected by this parasite. Out of total of 265 tick samples, R.sanguineus was highest (38.35%) and Haemaphysalispunctatahad the lowest (3/01%) frequencies. Regarding the vast distribution of R.sanguineus in the area, it seems that this tick may be the main vector of T.ovis in Lorestan province, Iran.