PCI-E 2.0 or 3.0

You need a pcie 3.0 Motherboard. honestly it doesn't matter. You wont see any noticeable performance increase and if your card is 3.0 and mobo is only 2.0 that is perfectly fine as its backwards compatible.

You can use a free utility called GPU-Z and check if its 2.0 or 3.0 or whatever.

Hope that helps.

im using MSI Z77 and i already enable PCI-E 3.0 in the BIOS. but GPU Z but the bus interface says PCI-E 2.0

Maybe, but frankly it won't matter if you have 2.0 or 3.0, it will be virtually almost same.

What CPU and card do you have? They are also determining factors in wether or not you can run at PCIe 3.0

im using ivy bridge cpu