Aiming at the problem of large number of micro ring resonator (MRR) required by current all-optical full adder, an optical full adder with three Cascaded MRR structures is proposed for the first time. In view of the fact that MRR is sensitive to temperature fluctuation and process variation, the MRR fault model is established. The mean error distance of reliability metric ofoptical full adder (OFA) is designed, and the influence of MRR single fault model on OFA is analyzed. Simulation results of insertion loss show that the proposed OFA architecture is superior to existing OFA architecture in general. Compared with the current scheme, the hardware overhead of the proposed OFA architecture is reduced between 50% and 70% . Experimental results show that the average error distance of scheme 1 and scheme 2 is large, while the average error distance of the proposed scheme is moderate. For the multi-bit binary full adder, the absolute value of the average error distance increases with the number of bits of the multi-bit binary full adder in the single fault model with the highest bit. For the single fault model with the lowest bit, the absolute value of the average error distance remains unchanged with the number of bits of the multi bit binary full adder. Physical verification and experiments based on Modelsim platform verify the correctness of the effect of MRR fault on the performance of full adder.