The energy levels of the odd-odd nucleus 86 Nb at low spins are calculated by using quasi-particles plus a rotor model. The distribution of the nearest-neighbour spacing and the spectral rigidity are studied. We find that the chaotic degree of the energy spectra increases with the increasing spin and reaches a maximum at I ＝ 10; then it decreases gradually for spins above I ＝ 10. The recoil term in the model Haniltonian makes the energy spectra slightly regular. The Coriolis force, however, makes the spectra chaotic and plays a major role in the spectral statistics of the odd-odd nucleus 86Nb.