what document required to apply for 90days business multiple visa?

Apart from your passport, application form and passport photo, you should provide the invitation letter from your trade partner or trade fair and a letter of dispatch issued by your company. Besides, a copy of your previous Chinese visas. If you don't have previous records, I am afraid it's unlikely that you will acquire a multiple type one.

is it true that i must have at least 5 entries to get multiple one?

It depends, as I know, you should have more than 2 business visas issued last year by Chinese embassy/consulate. You can confirm this with CVASC in your place.