OvTDM is a new transmission scheme that can obtain high spectral efficiency with very low threshold signal noise ratio (SNR) by using the inter symbol interference (ISI). Fano algorithm (FA) is researched in this paper to implement fast ML decoding at high spectral efficiency for OvTDM. Numerical results show that the complexity of OvTDM with FA has no relationship with the number of state which is lower than 15% of that of Viterbi algorithm and the bit SNR loss is under 2 dB. Moreover, OvTDM with FA can even outperform Shannon limit when spectral is above 6.7 bits/s/Hz.