Ionospheric delay is one of the error sources that must be considered in the propagation of navigation signal. Similar to GPS and Galileo satellite navigation systems, BD satellite navigation system also transmits ionospheric parameters in its navigation messages for the real-time correction of ionospheric delay in users’ terminal. With the completion of BD regional navigation system at the end of 2012, BD can provide PNT service in Asia pacific region. Nowadays. As BD is developing from the regional coverage system to the global coverage system, the ionospheric model that is fit for regional coverage must be changed. In the stage of BD regional system, the model of Klobuchar 8 is adopted which is almost the same as that of GPS. The Klobuchar model that proposed in 1987 by Klobuchar is based on trigonometric cosine function. Although GPS and BD apply the same ionosphere model, they are different in several aspects, such as the generation way of ionosphere parameter, update interval, coverage area and correction accuracy. The Klobuchar model of BD is generated based on the dual-frequency measurements from the ground regional monitor station network. Limited by the regional distributed monitor stations and lacking of long-term accumulation of ionosphere data, the model parameters of BDS is updated every two hours and only applicable for the northern hemisphere. Many research results indicate that BDS Klobuchar model can reach meanly more than 70% correction ratio of ionospheric delay which is more effective than that of GPS Klobuchar model especially in the mid latitude region of northern hemisphere. China Satellite Navigation Office published issued the interface control documents for the global public service signals of B1c and B2a of BDS on December 27, 2017. The BD GIM9 model for the global correction of ionospheric delay is given in the latest ICD. The differences between the regional BDK8 and the global BDGIM9 model will be explored in this paper including the physical meaning, mathematics model, update interval and correction accuracy. The improvements of BDGIM9 model relative to BDK8 will also be summarized.