The invention provides a measuring system for a secondary current of an induced voltage adder, a marking device and a method thereof. The measuring system is characterized in that a plurality of B-dot arrays are uniformly distributed along an angular direction on inner and outer cylinders of a transition section between IVA secondary inducing chambers, so that the angular directional distribution of the secondary current at an outlet of each level of IVA secondary inducing chambers can be measured. Due to the special electric structures of the inducing chambers, the inducing chambers are replaced by coaxial marking external cylinders added on the positions of the original inducing chambers in the marking for B-dot probe arrays, so that the current passing by the B-dot probe arrays is uniform along the angular direction. A current closed loop is formed by the marking external cylinders and the transition connecting sections. At the secondary tail end, coaxial fast pulse current sources are adopted for providing uniform injection current, a current measuring coil sleeved on a grounding end is utilized to monitor the current parameters of the pulse sources and the B-dot probe arrays of the inner and outer cylinders of the secondary are marked.