How long will you stay in China and HK?

maximum of 2weeks
please where can i get it?

Mrs.dike, if you don't have business partner in Hong Kong or Mainland China, you can't get the invitation letter, you need a visa to Hong Kong and Mainland China. If you go to Hong Kong for business, you should have Photocopy of proof of the proposed business visit to Hong Kong, e.g. letter issued by the applicant's employing company to confirm his/her proposed business activities in Hong Kong or invitation letter issued by a local company

For the China business visa application, the visa notification from an athorized governmental unit is required, you business partner can help you to get it then send it to you for visa application.

please i dont have a buisness partner and this is my first time to china.please how do i get an invitation letter.

You can't get the Invitation Letter if you don't have business partner. You can ask a visa agency to help you to apply for Hong Kong visa and China visa. Please have a try, but be careful you are cheated by the visa agency. My opinion is that you can apply for tourist visa and ask an international travel agency in Hong Kong and Mainland China to issue you original Invitation letters.