The Executive has sought the devolution of tax powers for years.
It is committed to matching the Republic of Ireland's 12.5% rate by 2018.
But Mr Ó Muilleoir said they may need to consider reducing it below that.
The UK corporation tax rate is currently at 20%.
However, the Chancellor, George Osborne, is now pointing to a rate "below 15%" to attract businesses when the UK leaves the EU.
Speaking on BBC Radio Ulster's Nolan Show on Tuesday, Máirtín Ó Muilleoir, said: "I think he has put a horse and carriage through our policy.
"There's no doubt about that because we had two reasons for it, one was to be different from the British rate and be the same as the rate in the south of Ireland.
"We know, especially in north America, that Ireland is viewed very favourably and actually they view Ireland as one island, they are not big on borders.
"And if we had have been able to say, the tax rate is the same across the island, I think that would have been compelling, that's no longer true.
"Unless we go for an different strategy and reduce it ever further, and that will need to be considered."
The Finance Minister Máirtín Ó Muilleoir has said that the Chancellor George Osborne has driven a "horse and carriage" through Stormont's corporation tax cut plans.