Due to the development of economy and higher living quality, people pay more attention to leisure activities. Tennis is a leisure exercise suitable for teenagers, middle-ages and elders. The suitable age is from three years old (The famous tennis player, Agassi began to play tennis at three) to eighty years old (Mrs. LIU, Shiang-ku still plays at the Evergreen contests though she is at eighties). Furthermore, most tennis courts are located at fresh air and beautiful places. Playing tennis is an enjoyable sports.