I would like invite my parents to visit USA but do I need write letter to USA embassy too?

You need to write in more details before some one can answer your question like what is your status in US and why do your parents want to visit US?

Thank you for reply chappaljutta ji .my legal status green card (more than 5 years).I want apply them for Toursit Visa.

Though you will be submitting I-134 (affidavit of support) with other documnets, it is nice to wirte a leltter addressing the consulate general that you will be taking care of all the expenses of your parents while they are in US. This will certainly make your case look strong.

Regardles of your status , it's always good to have a letter to Consulate General of America ( or whoever concerned). State the following (minimum) in your letter ( like chappaljutta mentioned):

• your reason for inviting them.
• you are the sponsor for your family and are responsible for all financial expenses.
  

~GooDLucK

Thank you for all.