The complexities of JavaEE Web application system easily lead to many performance problems which are mainly caused by servers. The systematic diagnosis process and solutions for servers are presented based on the basic principal described by“From outside to inside, from surface to core, breakdown step by step”. Three angles of view such as user experiences, resources and components are presented to drilldown the problems step by step. Then the strategies of performance diagnosis are discussed from four aspects including user transactions, system resources, Web resources and page components. Some good experiences are put forward for similar projects of performance diagnosis.