The dry shrinkage and pore structure of cement mortar with steel slag powder(SSP) and steel slag sand(SSS) at early age were investigated. The results indicate that SSP and SSS can both decrease the early aged dry shrinkage of cement mortar, especially at their dosages being no more than 30% (by mass). With the variation of particle size distribution, the influence of SSS on the early aged dry shrinkage of cement mortar is somewhat different, but there exists more significant improvement of SSS with particle size smaller than 2.5mm. The improvement on the early aged dry shrinkage is due to the fact that both SSP and SSS can improve the pore structure and the pore size distribution to decrease the porosity of cement mortar. Besides, SSP demonstrates much better improvement on the early aged dry shrinkage and pore structure of cement mortar than SSS. However, there is no significant improvement on the early aged dry shrinkage and pore structure when SSP and SSS are simultaneously mixed in cement mortar.