You both must use the same deduction - either standard or itemized.
The way the rule reads is that if one spouse itemizes their deductions, then the other spouse is ineligible to take the standard deduction. That spouse must then either itemize or take no deduction at all. Applying to your facts, if your husband itemizes his deduction and you take the standard, the IRS will send you a letter disallowing your standard deduction and it will likely increase your tax liability. So, you really want to make sure you are on the same page before filing your return.
Now, just because he has a lot of business deductions, that doesn't mean he might not still use the standard deduction. If he is self-employed, then he is using a Schedule C to report his business income/expenses. These expenses are reported separately from any standard/itemized deduction. Some common itemized deductions are mortgage interest, property taxes, medical expenses, charitable contributions, and state/local taxes. So, if there aren't enough of those itemized deductions, then the standard could work out best for him also. Either way, you will both need to end up taking the same type of deduction when filing separate.
Page 24-25: Itemized deductions with MFS
