The study started on July 2021 and will last 1.5 years. Primary APS patients with three positive aPL and extra-criteria manifestations with be enrolled. This is a single-arm pilot study. Telitacicept 160mg once a week for 24 weeks will be added on traditional antithrombotic and immunosuppressive treatment. Patients will be followed on week 12 and week 24. The primary endpoint is new thrombotic event. The secondary endpoints are improvement of extra-criteria manifestations, and titer change of aPL.