The high order harmonic generation by two-colour coherent laser fields of arbitrary polarization (1ω plus 2ω or 3ω) is studied systematically. The results show that a single circularly polarized field can not emit high harmonics, under some conditions some order harmonics can be enhanced and some can be eliminated or decreased. The high order harmonic generation has a strong dependence on the ellipticity of the fundamental field and the mixing of different fields.