This study is a multicenter, open label, fixed dose exploratory clinical trial with an expected enrollment of 30 subjects. The main objective is to evaluate the safety of targeted BCMA autologous CART cell injection in the treatment of recurrent or refractory light chain amyloidosis in subjects, preliminarily verify the effectiveness of targeted BCMA autologous CART cell injection in the treatment of recurrent or refractory light chain amyloidosis in subjects, and explore the pharmacokinetic, pharmacodynamic, and immunogenic characteristics of targeted BCMA autologous CART cell injection after reinfusion.