Background and Aim: Due to the effects of herbs in the prevention of kidney stones, the present study aimed at assessing the effect of aqueous eryngium campestre on the prevention of pathologic alterations caused by calcium oxalate crystals induced by ethylene glycol in the cortex and medulla of rats’kidneys. Materials and Methods: To conduct the study 40 male Wistar rats, weighing 200 – 250 gr were randomly divided into 5 equal groups; i.e. the healthy control group that just received water, the negative control group receiving water with 1% ethylene glycol, the prevention groups, which in addition to 1% ethylene glycol in water were daily gavaged with 100 mg/kg, 200mg/kg, and 400 mg/kg of the plant extract. After 30 days all rats were killed and slides from each one’s kidneys were prepared. The slides were stained applying H/E method and the number of their calcium oxalate crystals was checked. Results: It was found that there was a significant difference between the number of their calcium oxalate crystals in the control health and negative groups (P<0.05). But, in the prevention group gavaged 100 mg/kg there was no significant difference with the negative group, (P>0.05). However, in the 200mg/kg prevention group compared to the negative control one there was a significant difference in reducing the number of the crystals (P<0.05). But in 400mg/kg the prevention group there was no significant difference with the negative control group (P>0.05). Conclusion: It was discovered that aqueous extract of eryngium campestre is effective in preventing the accumulation of calcium oxalate crystals in the kidney.