Marriage between bangladeshi girl and indian boy

you both got to marry according to foreign marriage act as one of you is a citizen of india and other a foreign citizen.if you both are indians and if you both belong to different religions then you can marry under special marriage act

I disagree with Saravanan and I completely agree with Kapil Chandana.  Since the marraige to be performed is under Special Marraige Act, caste or religion is immaterial.  There is no need to change the religion.

The Special Marriage Act was enacted to provide a special form of marriage by any person in India and all Indian nationals in foreign countries irrespective of the religion either party to the marriage may profess.

Conditions relating to solemnization of foreign marriages.under foreign marriage act—A marriage between parties one of whom at least is a citizen of India may be solemnized under this Act by or before a Marriage Officer in a foreign country

in this case the boy is a indian national and the girl is bangaladeshi. so i have a doubt about how they can marry under special marriage act.kindly clarify sir

Yes, I agree with saravanan. Sec. 4 of Foreign marraige act is relavant provision.  I correct my earlier opinion. I invite the comments of Mr. Kapil Chandana on this aspect. 

Also clarify me that If both are foreign citizens and if they would like to get registered marraige in india, under which Act it should be performed?

The Foreign marriage Act, 1969 will give you the complete details including the procedure to solemnize the marriage, issue of notice and registration details.  You may go through the said law and then consult a local advocate if you dont understand the terms used in the law.