The effect of polypropylene fiber on dry-shrinkage ratio of cement mortar was studied. The experimental results show that, polypropylene fiber mixed into cement mortar can decrease its dry-shrinkage ratio; and with increase of volume fraction of polypropylene fiber, the dry-shrinkage ratio of cement mortars are decreased firstly, and then increased, it reaches the lowest value with the fiber volume fraction of 0.20%; Polypropylene fiber length, diameter, methods of surface modification and shape of cross-section all have some effects on the dry-shrinkage ratio of cement mortar, and as for the fiber parameters discussed in this paper, the cement mortar reinforced with polypropylene fiber which are longer, finer, or have greater specific surface area, will have smaller dry-shrinkage ratio.