Abstract: In the argumentation and design phase of low-band earth-satellite links, the occurrence probability prediction information of low-latitude ionospheric scintillations is needed to analyze link margin and system availability. Based on the historical observations of UHF-band and L band ionospheric scintillations, the variation characteristics of ionospheric scintillation occurrence with time, latitude, season and solar activity are presented in detail. After the key technology of probability distribution function (PDF) modeling of ionospheric irregularity intensity C_kL is broken through, an occurrence probability prediction model of ionospheric scintillation for the low-latitude region is built. The occurrence probabilities of a specified ionospheric scintillation S₄ index could be predicted by entering the positions of transmitter and receiver, time, the predicted sunspot number and signal frequencies, which could provide the essential data for the margin design and system availability analysis of low-band earth-satellite links.