The powder X-ray diffraction patterns of LaFe11.5Si1.5 compounds annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h) show that a large amount of 1:13 phase begins to form in LaFe11.5Si1.5 compound annealed at 1423 K (5 h).In the temperature range from 1423 to 1523 K,α-Fe and LaFeSi phases rapidly decrease to form 1:13 phase.LaFeSi phase is rarely observed,and the most amount of 1∶13 phase is obtained in the compound annealed at 1523 K (5 h).With the annealing temperature increasing to 1573 and 1623 K,LaFeSi is detected again in the LaFe11.5Si1.5 compound.According to the results of annealing at different high-temperatures,the La1-xCexFe11.5Si1.5 compounds are annealed at high temperatures of 1373 K (2 h) + 1523 K (5 h).The main phase is NaZn13-type phase,and the impurity is a small amount of α-Fe in La1-xCeFe11.5Si1.5 compounds with 0 ≤ x ≤ 0.35,and there is a large amount of Ce2Fe17 phase in La0.5Ce0.5Fe11.5Si1.5.It indicates that the substitution of cerinm atoms for La in LaFe11.5Si1.5 compounds has limit.At the same time,the substitution of Ce for La has large effect on magnetocaloric properties.With increasing Ce content from x =0 to x =0.35,the Curie temperature decreases linearly from 196 to 168 K,the magnetic entropy change increases from 16.5 to 57.3 J.kg-1.K-1 in a low magnetic field change of 0-2 T,and the thermal hysteresis also increases from 3 K to 8 K.