Magnetic properties and magnetocaloric effects of La1-xRxFe11.5Sil.5 (R=Pr, (0 ≤ x ≤ 0.5); R = Ce and Nd, (0 ≤ x ≤ 0.3)) compounds are investigated. Partially replacing La with R = Ce, Pr and Nd in La1-xRxFe11.5Si1.5 leads to a reduction in Curie temperature due to the lattice contraction. The substitution of R for La causes an enhancement in field-induced itinerant electron metamagnetic transition, which leads to a remarkable increase in magnetic entropy change △Sm and also in hysteresis loss. However, a high effective refrigerant capacity Rceff is still maintained in La1-xPxFe11.5Si1.5. In the present samples, a large △Sm and a high Rceff have been achieved simultaneously.