La(Fe, Si)₁₃H_Y based alloy is regarded as the candidate of the room temperature magnetic refrigeration materials. However as the poor mechanical property of the hydride which is difficult to be used in the magnetic refrigerator. How to prepare the magnetic refrigrant with large magnetocaloric effect is the key problem to be solved. In this paper La_0.8Ce_0.2Fe_11.51Mn_0.19Si_1.3master alloy was prepared by medium frequency induction furnace and annealed, followed by milling to powder. The alloy podwer was hot pressed at 650 ℃, 850 ℃ and 1050 ℃ respectively. The resulted La_0.8Ce_0.2Fe_11.51Mn_0.19Si_1.3alloy was cut into plates and then hydrogenated until saturated. The phase constitution, microstructure and magnetocaloric effect of samples was determined by XRD, SEM and VersLab. The porosity is the lowest and the volumetric magnetic entropy change is the alrgest (144.7 mJ/cm^₃?K) for the sample hot pressed at 1050 ℃. The Curie temperature increase to near room temperature, the large magnetocaloric effect of the first order phase transition is still maintained for the sample hot pressed at 1050 ℃ after hydrogenation. No cracks on the surface are found on the hydride and keep integrity.