In　this　paper,　we　proposed　a　computationally　efficient　sphere　decoding　method　for　MEMO　OFDM　system　with　the　aid　of　HARQ.　This　is　a　cross　layer　design　scheme　which　adopt　the　SNR　updating　information　based　on　retransmission　operation　to　reduced　the　search　radius　of　sphere　detector,　it　leads　the　low　complexity　of　sphere　detection.　Further　more,　a　modification　of　sphere　decoding　is　proposed　to　handle　non-rectangular　constellations,　which　is　more　effective　for　universal　modulation　signaling.