I want to use a 13 dBi antenna for my Xbee but I am not sure if the xbee could support that antenna or not.
Assuming that you are in the US, here is the page from the manual on FCC certified antennas: http://www.digi.com/resources/documentation/digidocs/90002173/Default.htm#reference/r_certs_xbee_900hp_antennas.htm
It looks like a 13 dBi antenna will require a certain amount of cable loss to be legal under FCC restrictions.
As to whether the XBee can physically support it, the answer is yes.