The (R, Ce)-Fe-B magnets have been successfully industrialized in recent years. The mechanical property of sintered permanent magnets is one important aspect of their comprehensive performances, which directly influences the service reliability and the production cost. In this work, the bending strength, fracture toughness, Vickers hardness and brittleness index of commercial (R_1-xCe_x)_30.5’31.5Fe_bal.-B₁M₁ (mass fraction, %) magnets with different Ce contents have been investigated. The microfractures of the magnets were observed by SEM equipped with EDS. It shows that the bending strength and the fracture toughness of (R, Ce)-Fe-B magnets have a downward tendency with increasing Ce content x, while the Vickers hardness of the magnets varies irregularly with Ce content. The optimum mechanical properties have been obtained in the (R_1-xCe_x)_30.5~31.5Fe_bal.-B₁M₁ magnet with x=0.15; the bending strength, fracture toughness and brittleness index of the magnet with x=0.15 are obviously superior to those of the ordinary sintered Nd-Fe-B magnets. Some flocculent oxide phases have been discovered in the (R, Ce)-Fe-B magnet with x=0.15. The flocculent phases may absorb part of energy during crack propagating, and reduce the stress concentration at a crack tip, which is beneficial to strengthening and toughening of (R, Ce)-Fe-B magnets. However, the mechanical properties are obviously worse for the magnet with x=0.45 (Ce/ΣRE=45%). That is probably because the microstructures of the magnet with x=0.45 become deteriorated, in which abnormally large grains have been observed. The results confirm that the fracture mechanism of sintered (R, Ce)-Fe-B magnets with different Ce contents mainly appears intergranular fracture.