Abstract: The tidal variabilities are studied by using the data from the 14th July to 14th August in 2006, observed by the 3 MHz and narrow beam MF radar located at the Andoya Rocket Range (69.14ºN, 16.02ºE). The results indicate that, the intensity of the zonal and meridinal components of the diurnal and semidiurnal tides has experienced the process of weak to strong and again to weak in the height range 78~94 km. This shows that, the new tides may be produced due to the instability induced by the interactions between tides and other waves during the upward propagation of tides, and again the new tides propagated upward stably. These phenomena may also be caused by the momentum deposition due to the breaking gravity waves or other waves. The tidal amplitude varies not only with increasing height, but also with time evolution. The variability of the diurnal tidal amplitude is very strong and varies by a factor of 3 in some days. Based on the recent results, the gravity waves instability and breaking are one of the causes to induce the tidal variability. Furthermore, The comparative results between the observation and GSWM-00 model shows that, the model can forecast results for the amplitude and phase of the diurnal tide are very good, but it isn't very ideal for the semi-diurnal tide's.