Recently, the study of nanocomposites has attracted much attention, but the powder isdifficult to be homogenized and nanoparticles are not well distributed when nanophase isintroduced into matrix via general mechanical mixing. The in situ formation of AlNsubmicron particles in Al_2O_3 matrix has been explored to prepare AlN-Al_2O_3 composite bymeans of reaction-bonding method. Recently, the study of nanocomposites has attracted much attention, but the powder is difficult to be homogenized and nanoparticles are not well distributed when nanophase is introduced into matrix via general mechanical mixing. The in situ formation of AlNsubmicron particles in Al 2 O 3 matrix has been explored to prepare AlN -Al_2O_3 composite bymeans of reaction-bonding method.