There you go!

https://www.embibe.com/exams/bitsat-previous-year-question-papers/

I am providing you the link of the website but it only have the papers of 2008-2013 to get the lastest year papers apart from online I suggest you to go for books instead like BITSAT 13 years topic wise solved papers 2003-2-17 by disha publication you can easily get this book from flipkart or any book market near you as the question and solutions in these books have more authenticity then the papers they provide you online as they aren't available by the original website we can't be absolutely sure about their authenticity. Here are the links for both,

https://www.embibe.com/exams/bitsat-previous-year-question-papers/

https://www.flipkart.com/bitsat-13-years-topic-wise-solved-papers-2017-2005-5-online-mock-tests/p/itmezgzuvagsgvhy?gclid=EAIaIQobChMIkczKzcjQ2gIVCWoqCh0lHgUoEAQYASABEgJXkvD_BwE&pid=9789387045026&lid=LSTBOK9789387045026Z8CGSC&cmpid=content_book_8965229628_gmc_pla&tgi=sem%2C1%2CG%2C11214002%2Cg%2Csearch%2C%2C170219493259%2C1o1%2C%2C%2Cc%2C%2C%2C%2C%2C%2C%2C&s_kwcid=AL%21739%213%21170219493259%21%21%21g%21299142545466%21&ef_id=Wr0XuQAAAFuDpn4Z%3A20180423140615%3As

Good Luck!!.