AAAA, please check this website, hopefully this will help you. http://this.isfrom.us/pages/parents-invitation or simply google it. There are so many blogs related to the parents invitation.

So far I know, following documents are needed:

• Letter to Embassy asking the consular to issue visitor visa to your parents
• Invitation Letter to Parents
• Affidavit of Support (I-134)
• A Certificate showing your relation to your parents (with pictures)
• Employment Letter (with your salary, bonuses, when you started working with them etc.)
• Bank Statement (ask bank to provide you a letter for immigration purpose)
• Tax Return Documents (If you have filed any)
• Copies of recent Pay Stubs (Probably 3-4 pay stubs)
• Copy of H1-B Documents (not sure if original is required or a copy will work)

Your parents will have to show the evidence that they have strong family ties in Nepal and will return back after the visit in interview.

Hope this helps.