The　PCT　properties　and　hydriding/dehydriding　kinetics　were　simulated　for　LaNi4.7Al0.3　under　quasi-isothermal　and　variable　pressure　conditions.　An　ideal　kinetic　expression　for　the　hydriding/dehydriding　reaction　is　an　important　tool　in　the　designing　process　of　reaction　unit.　This　paper　is　based　on　PCT　polynomial　equation　and　nucleation　and　growth　model,　and　appropriate　model　equations　were　obtained　for　hydriding/dehydriding　reaction　of　LaNi4.7Al0.3　hydrogen　storage　alloy.　There　was　a　large　slope　in　the　PCT　plateau　of　the　alloy.　The　plateau　was　divided　into　three　regions　according　to　hydrogen　content　of　hydriding/dehydriding,　and　enthalpy　and　entropy　values　are　calculated　for　each　regions　using　Van＇t　Hoff　equation.　The　results　show　that　the　activation　energy　value　was　Ea=32　kJ/mol,　and　the　Avrami　index　n　were　within　the　narrow　range　of　1.1-1.33　in　the　model　equation.　The　theoretical　curves　and　the　experimental　data　show　a　good　agreement.　The　mechanism　of　hydriding/dehydriding　changes　from　one-dimensional　nucleation　and　growth　in　the　prior　period　to　lower　diffusion　in　the　later　period　for　controlling　reaction　process.