This paper proposes one method for precision assessment of broadcast ionospheric model of GNSS,performing by using real ionospericdelay as a reference based on base stations.It can decide the amount of ionospheric delay by base stations spread all over the world precisely,then statistic the precision of broadcast ionospheric model of GNSS station by station.As shown in results: the correction percent of broadcastionospheric model of BDS/GPS/GAL normally is 60% above,and the RMS is better than 2.0m.In addition to,the correction percent of BDS is higher than GPS and Galileo,better than 75% in China.