HONG KONG, March 18 (Reuters) - Private equity firm KKR & Co LP, search engine Baidu Inc and hedge fund Coatue said on Wednesday they will jointly invest $170 million in Chinese online used-car auction firm Uxin, aiming for a piece of the booming used-car market.

Uxin will use the funds to expand a newly launched platform where auto retailers sell used cars to individuals, the companies said in a joint statement.

China, the world's second-largest economy, had 368 billion yuan ($59 billion) worth of transactions in the used-car market in 2014, up 26 percent from the previous year, the statement said, citing figures from the China Automobile Dealers Association. ($1 = 6.2365 Chinese yuan renminbi) (Reporting by Elzio Barreto; Editing by Muralikumar Anantharaman)