I'm starting an ecommerce business from my origin country and I will sell products in the USA . I need to open an US bank account in my business name. I already have an LLC and I need to know is it possible to open this bank account with a B-2 Visa?
Generally, to open a business account in the USA, you need to prove that the business exists as both a physical and legal entity, that it's set up appropriately with the IRS, and that you (personally) have proof of identification.
To prove the existence of the business, you'll need to provide articles of incorporation or some other legally binding documentation that establishes the business's structure and identity. Some banks may want other documentation about the business, depending on the structure (i.e. if there are multiple owners, they will want to see something describing their roles). You'll also likely need to prove that the business has a valid physical address in the US - via utility bills with that address on them, or (ironically) bank statements or other legitimate mail to a US address. Proving the address can be a bit of a chicken-and-egg game, because you may not yet have utility bills or other official mail if you don't have a bank account. Some banks will accept your EIN paperwork as proof of address. Proof of your own identity can usually be done with your passport.
The other major requirement is proving your relationship with the IRS. Basically, the bank will want a tax identification number (TIN) of some kind. If you are set up "doing business as" yourself, and you have an SSN, you can use that. If you don't have a US SSN, you can obtain an ITIN (individual tax ID number) for yourself. Or, if not operating as a sole proprietorship, you will need to obtain an EIN (employer identification number) for the business. Obtaining an EIN is easier if you, personally, have a TIN already - if you do not have a TIN, you cannot apply for an EIN remotely, you'll have to do it in person.
dwizum's answer is great, but let me answer your specific question about the visa - which you might have asked on our Travel site.
Technically a B2 visa does not permit you any business activities, which this would count as. However in a lot of cases an application for a B2 gets a B1/B2 visa which combines the allowed activities of both. A B1 visa would certainly let you set up a bank account.
A bank probably isn't going to check that you have the right visa to open an account, but if you have a strict B2 visa it might be safer to apply for a B1.