主要是想換的房子超過3個時要用 200% rule Google 吧

If the taxpayer wants to identify more than three investment properties (also known as the 1031 exchange 3 property rule), he can use the 200% rule. This rule says that the taxpayer can identify any replacement properties as long as the aggregate fair market value of what he identifies is not greater than 200% of the fair market value of what was sold as relinquished property.