Is that true that the level of mhcet 2018 will be nearly equal to jee main level.

No, it won't be. At best they might ask a few more conceptual questions, but even those questions will be below par in difficulty if compared to JEE mains.
See the questions in MHT-CET are mostly fact based, while Jee mains tests your conceptual understanding and builds on those concepts.
So if you have prepared well for the board exams, you will be covered for MHT-CET. While the same thing doesn't apply at all, for JEE Mains.