Abstract: Wind measurements obtained from Wuhan/China MF radar during winter 2001 are used to study the phase relationships between tidal horizontal winds in lower thermosphere. The tidal initial phases in any time window are uniformly defined in radians. The meridional and zonal initial phases of each tide exhibit a similar time variation trend at each height and this induces a near phase difference at three consecutive heights. However, in most of the 14 days, △φ4 and △φ12 are quasi-quadrature while △φ8 is unexpectedly quasi-in-phase. The appropriate tidal meridional and zonal quadratic phase coupling （QPC） equations are estimated respectively. The supposed terdiurnal phases and those observed agree well. By subtracting the estimated tidal zonal QPC equation from the meridional, a tidal phase difference correlated equation is obtained. The supposed terdiurnal phase differences and those observed again agree with each other. Within the 14th time window, all the three tides are generally elliptically rather than circularly or linearly polarized. However, both △φ24 and △φ12 in this window are quasi-quadrature at all heights while △φ8 are quasi-in-phase at 92.0 and 94.0km. So the estimated tidal QPC equations, the deduced tidal phase difference correlated equation, the observed terdiurnal quasi-in-phase phase differences and the typical tidal polarization plots are all indications of real QPC between the observed 24, 12 and 8 h tides.