We　have　studied　systematically　the　effects　of　temperature,　time,　and　pressure　on　the　process　of　hydrogen　absorption　in　LaFe11.5Si1.5　compound.　Results　show　that　hydrogen　absorption　can　increase　the　lattice　parameter　of　the　compound　without　changing　its　crystal　structure.　The　LaFe11.5Si1.5H1.6　compound　can　be　prepared　at　a　hydrogen　pressure　of　0.0987　MPa　at　423　K　with　uniform　distribution　of　hydrogen.　Hydrogen　absorption　can　also　increase　the　Curie　temperature　obviously,　decrease　the　thermal　hysteresis　and　maintain　the　magnetic　entropy　change　at　a　high　standard.　With　prolonged　exposure　time　in　air,　the　variation　of　the　Curie　temperature　and　magnetic　entropy　change　of　LaFe11.5Si1.5H1.6　compound　are　very　small,　implying　that　the　magnetic　thermal　performance　of　hydride　alloy　has　a　good　time　stability.