Unitary space-time modulation(USTM) is well tailored for flat fading channels where neither the transmitter nor the receiver knows the fading coefficients. In this thesis, we propose a new schemes of unitary space-time modulation. Different from the past proposed systematic codeword, we consider the unitary space-time codeword which don’t have the algebraic structure. Then we use asymptotic union bound and diversity product to search unitary space-time codeword.