Abstract: We reconsider pair annihilation processes of dark matter in the framework of universal extra dimensions, in which all the standard model particles propagate. In such scenarios, as a consequence of Kaluza-Klein (KK) parity the first excitation mode of the B boson is a viable candidate of cold dark matter, and the Fourier expanded modes are almost degenerate in mass at each KK level. We point out that the KK dark matter annihilation cross section is significantly enhanced due to the threshold singularity in the non-relativistic limit. Consequently the predicted positron flux is increased compared with that at the tree level. The operative and future positron experiments will serve as good probes to distinguish physics beyond the standard model.