Abstract: As an important task of multi-relational data mining，multi-relational classification can directly look for patterns that involve multiple relations from a relational database and have more advantages than propositional data mining approaches.According to the differences in knowledge representation and strategy，the paper divids multi-relational classification approaches into ILP，graph-based and relational database-based classification approaches and discusses each relational classification technology，their characteristics，the comparisons and several challenging researching problems in detail.