To balance the utilization of rare earth (RE) resource and develop Ce-based permanent magnets with high performance/cost ratio, the role of La substitution in the melt-spun (Ce1-xLax)(y)Fe14B (x = 0-0.4, and 0.5; y = 2-4) alloys has been investigated. It has been confirmed that the hard magnetic properties of Ce-based magnets can be effectively enhanced by partial substitution of La. The maximum (BH)(max) of (Ce,La)-Fe-B alloys can be obtained at a Ce:La atomic ratio of 7:3. The lattice parameters and Curie temperature of the hard magnetic (Ce/La)(2)Fe14B phase increase linearly with increasing La content. Three different alloy systems with y = 2, 2.5 and 3 show similar behavior of magnetic properties dependences on La. In the RE-rich compositions, La substitution for Ce can effectively inhibit the precipitation of the CeFe2 phase. A solid solution, Ce(La) phase with a space group of Fm-3m, appears in the (Ce0.7La0.3)(y)Fe14B alloys with y >= 3.5. A good combination of magnetic properties with H-cj = 345 kA/m, J(5T) = 1.03 T, J(r) = 0.60T, and (BH)(max)= 6.3 MGOe is obtained in (Ce0.7La0.3)(2.5)Fe14B alloy. In addition, 30 at.% La substitution for Ce can significantly refine the grains, resulting in the enhancement of exchange coupling interaction. The present finding is beneficial for designing new and low-cost magnetic materials.