I want to get product Buybox price based on product ASIN.
Is there any API available in Amazon ?
The ItemLookup call of the Product Advertising API has a ResponseGroup named Offers which will allow you to get the buy box price (or, if nobody has the buy box, it will return the lowest offer).
According to this question it seems there is no way to tell if a returned price is actually the buy box price or just the lowest offer.
Alternatively, if you are a seller on Amazon, you could also use the GetCompetitivePricingForSKU call of the MWS Products API.