Introduction: Cancer is a deadly disease, caused by benzopyrene which found in cigarettes. The moderate intensity of exercise can affect cancer growth, but how the role it to p53 mutant is not clear. This research proved the expression of p53 mutant in Mus musculus by moderate intensity of exercise. Method: Eighteen animals, were divided into three groups namely, group A, injected by oleum olivarium in the upper buccal mucosa and not given moderate intensity of exercise and benzopyrene; group B, injected benzopyrenes in the same regio, not given moderate intensity of exercise; group C injected benzopyrenes in same region, given moderate intensity of exercise. Moderate intensity of exercise given 3 times every week for 3 months. Oleum olivarum and benzopyrene injection, was given 3 times every week for 1 month, starting at week 5. At the beginning of the 13th week, a bend was taken in the right upper buccal mucosa, then the tissue was processed, painted by immunohistochemical methods. p53 mutant expression was determined by looking at preparations, using an Olympus light microscope with a magnification of 400x. p53 mutan expression was observed in 10 different visual field, then the mean was taken. Result: There were differences in p53 mutant expression in the three groups (p= 0.000), and the highest expression was in group B. Conclusion: The moderate intensity of exercise could decrease p53 mutant expression on squamous cell epithelial of oral Mus musculus.