The effects of volume fraction, length and geometric shape of polypropylene fiber on the anti-dry-shrinkage cracking property of cement mortar were tested by the ring test method. The experimental results show that trefoil polypropylene filament fiber can obviously increase the anti-dry-shrinkage cracking property of cement mortar in hardening stage. The more the fiber is mixed, the better the anti-dry-shrinkage cracking property of cement mortar are improved. Polypropylene fibers with different shapes of cross-section have different effects on the anti-dry-shrinkage cracking of cement mortar. The cracking width of cement mortar reinforced by polypropylene fiber with trefoil cross-section is smaller. The longer the length of trefoil polypropylene filament fiber, the better the anti-dry-shrinkage cracking property of cement mortar. The mortars reinforced by trefoil polypropylene filament fibers treated with different surface-modifications have better anti-dry-shrinkage cracking property, in which the anti-dry-shrinkage cracking property of cement mortar reinforced by the polypropylene fiber treated with oxidant is best.