The　Ni/Mg/Al　catalysts　were　prepared　from　the　calcination　and　reduction　of　hydrotalcite-like　compounds　containing　Ni,　Mg　and　Al,　and　applied　to　the　steam　reforming　of　tar　from　pyrolysis　of　biomass.　The　dependence　of　the　composition　and　reduction　pretreatment　conditions　on　the　catalytic　performance　was　investigated.　It　is　found　that　the　Ni/Mg/Al　catalyst　with　optimized　composition　of　Ni/Mg/Al=9/66/25　exhibited　much　higher　activity,　resistance　to　coke　deposition,　and　stability　than　Al2O3-　and　MgO-supported　Ni　catalysts.　The　catalyst　characterization　using　XRD,　TPR,　N2　and　H2　adsorption,　and　TEM　indicates　that　the　Ni/Mg/Al　catalyst　after　the　reduction　has　a　nanocomposite　structure　of　Ni　metal　particles　(about　8.5nm)　and　Mg(Ni,　Al)O　particles　(about　11.5nm).　Even　after　the　catalytic　use,　the　nanocomposite　structure　was　maintained.　High　performance　of　the　Ni/Mg/Al　catalyst　including　the　suppression　of　the　aggregation　of　the　metal　particles　can　be　caused　by　the　nanocomposite　structure.　©　2010　Elsevier　B.V.