The Chinese Academy of Sciences (CAS) became a new Ionosphere Associate Analysis Center (IAAC) of the International GNSS Service (IGS) since 2016. To take advantage of the multi-GNSS techniques for global ionospheric monitoring, new signals of BeiDou and Galileo have been included in CAS’s ionospheric analysis in addition to the legacy signals of GPS and GLONASS. In this contribution, the recent multi-GNSS ionospheric research activities conducted at CAS IAAC are presented. For multi-GNSS code bias handling, the routine generation and delivery of CAS’s multi-GNSS differential code biases (DCBs) started since the third quarter of 2015. Recently, GNSS code biases are processed in the concept of observation-specific biases (OSB). The multi-GNSS DCBs and OSBs are routinely generated and analyzed using regional (EPN) and global (IGS & MGEX) networks of GNSS receivers, respectively. For global ionospheric vTEC modeling, dual-frequency BeiDou and Galileo observations are introduced. In addition to the routine generation of rapid and final global ionospheric maps (GIMs), the real-time GIMs have been routinely generated and validated since mid-2017 using real-time GNSS data streams of the IGS. For ionospheric TEC irregularity monitoring, a new ionosphere activity index, rate of ROT change index (RROT), is developed to characterize the perturbation degree of the ionosphere. With multi-GNSS data obtained from around 2000 globally distributed GNSS permanent tracking stations, RROT and ROTI maps are routinely generated to analyze the occurrence and dynamics of the ionospheric TEC irregularity.