Dear Sir / Madam:
  Good day ! How are you?
  We hereby sincerely invite you and your company representatives to visit our booth at (地点) from April  to  (展会日期).
  Exhibition Center :   
  Booth Number :   
  Date :   to  
  Thank you very much for your attention.
  sincerely yours,
  [name] :邀请人名字
  [title] :邀请人公司