In this paper, a generalized likelihood ratio test (GLRT) is adopted to realize optimum detection for differential UWB signal. Supposeing the channel circumstance is unknown, receiver presented in this paper is structured as follows. First of all, the maximum likelihood (ML) estimation of channel is completed. And then statistic detection of differential UWB signal is practiced. The receiver is approved to be a kind of correlation receiver, and its local template signal is the average of received waveforms of the former symbol pulses. Based on this structure, Gaussian approximation is applied to output noise of the receiver, and in this way the analytical bit-error rate (BER) expressions for the receiver are derived. The GLRT receiver can serve primarily as a performance benchmark.