Chimeric antigen receptor T cell (CAR-T) therapy, a novel immunotherapy, shows great potential in the treatment of hematological tumors to conventional therapies. Great progress has been made over the past few decades in the treatment of relapsed/refractory acute/chronic lymphocytic leukemia. However, due to the lack of real-time monitoring methods, it is impossible to predict and assess the therapeutic effect during the treatment of blood tumors, and we cannot learn more about the complications and risks. Many challenges exist in the clinical transformation of CAR-T therapy. As a non-invasive method, molecular imaging shows promise on real-time visualization of the biological behavior of CAR-T in vivo. Tracking CAR-T by directly labeling or indirectly evaluation by reporter gene methods has achieved breakthroughs. This article reviews the current situation of monitoring systems of CAR-T therapy and future expectations for each of the methods presented.