Electroless　Ni-P　diamond　composite　coating　was　deposited　using　diamond　compound　particle.　By　introducing　the　concept　of　Avrami　exponent　nucleation　and　growth　kinetics　of　Ni-P　and　Ni-P-D　coatings　were　researched　during　isothermal　crystallization　process.　The　results　show　that　the　crystallization　beginning　time　of　Ni-P-D　composite　coating　is　less　than　that　of　Ni-P　coating　at　the　same　temperature,　but　its　crystallization　process　and　holding　time　are　longer,　which　means　the　diamond　in　the　coating　can　benefit　crystallization　beginning　but　hinder　the　process　of　crystallization.　The　crystallization　principles　of　Ni-P-D　and　Ni-P　coatings　are　identical,　the　Avrami　exponent　of　Ni-P-D　coating　is　2.87,　and　that　of　Ni-P　coating　is　2.91.