Abstract: In order to study the effect of adding magnesium oxide and polypropylene fibers on concrete strength and dry shrinkage，compressive strength and dry-shrinkage tests have been made with different amount of magnesium oxide and polypropylene fibers in concrete.The results show that the right amount of magnesium oxide or polypropylene fibers can increase the compressive strength of concrete.The shrinkage of concrete is compensated by adding magnesium oxide，but the high content of magnesium oxide can cause the increasing expansions of concrete.Adding the right amount of magnesium oxide and polypropylene fibers can increase the compressive strength，reduce early contraction of concrete.And polypropylene fibers can inhibit the constantly changes of concrete volume.Results can provide reference for proventing shrinkage and cracking of concrete tunnel lining in mining and water projects.

Key words: Concrete, Magnesium oxide, Polypropylene fibers, Crack resistance of concrete, Shrinkage