We propose a RRAM-based strong PUF with high area-efficiency and excellent MLA resistant ability. The switching randomness property and the resistance distribution property of RRAM are fully extracted as entropy source. A reconfigurable PUF structure is proposed to gain super exponential growth CRP space. A double XOR process is adopted to further enhance the ability against MLA with small area-overhead. Experimental results show excellent PUF metrics including intra-HD of 1.93%, inter-HD of 49.95%, uniformity of 49.02%. The whole CRP generation process takes 1.8us. Therefore, the proposed strong PUF is a promising candidate for IoT security authentication fields.