Abstract: By analyzing the observation data of UHF band scintillations recorded at Haikou station (geographic 20°N, 110°E) of the low latitude region in China from 2010 to 2017, we find that the occurrence is greater in the vernal equinox than in the autumn equinox in the eight years. Combined with the data from ionosonde observations, we conclude that the greater occurrence results from the asymmetry between the two equinoxes of the background F₂ region electron density and h'F during sunset.The enhanced background F₂ region electron density and the significant enhancement of h'F during sunset may be benefit tothe scintillation occurrences. Basedon the monthly occurrences of ionospheric scintillations, and the relationshipsbetween season and solar activity, a seasonal variation statistic model of scintillation occurrences with the equinoctial asymmetry is put forward, which could describe the seasonal variation characteristics of the scintillation occurrences, and it has important application value.