The ionospheric spread-F (SF) has been measured with different techniques,such as ground-based ionosondes,Global Positioning System (GPS) receivers,incoherent and coherent scatter radars,satellite borne topside sounders and in-situ measurements.According to the URSI handbook on Ionogram,SF derived from Digisonde data was divided into four types,i.e.,frequency SF (FSF),range SF (RSF),mixed SF (MSF),and branch SF (BSF).In this study,using the data of Digisonde at Hainan station from 2002 to 2007,we made a statistical analysis on SF.The results show that,at the low latitude station Hainan,never Brach SF was observed,but a new type of SF named strong range SF (SSF) was observed.The SSF has similar ionogram to RSF’s but the spread extends to such a high frequency so that the foF2 could not be determined.The SSF has properties such as: (1) It lasts at least one hour.(2) It mainly occurs at night and with a maximum occurrence before the mid-night.(3) It mainly occurs in the equinoxes and summer and with geo-magnetic index Kp =1.In the winter,its occurrence is very low.(4) It has a good correlation with L-band ionospheric cintillation.The Mechanism of SSF is discussed at this study,too.According to our study and the history of the Digisonde observation at other low latitude stations,we suggest that,at low latitude ionosphere,the Spread-F be divided into four types of FSF,RSF,SSF,and MSF whose are different from the IRSI handbook.