The More A-More B intuitive rule has become a research hotspot in the field of mathematical education in recent years. The intuitive rule of More A-More B is often reflected in students' responses to comparison tasks. In such tasks, students are asked to compare 2 objects that differ in a certain salient quantity A (where A[subscript 1] > A[subscript 2]) with respect to another quantity B (where B[subscript 1] = B[subscript 2] or B[subscript 1] < B[subscript 2]). Despite the fact that many students have the knowledge and skills needed to solve these tasks correctly, they tend to intuitively yet incorrectly argue that B[subscript 1] > B[subscript 2]. In a series of 4 experiments, the present study examined the general applicability of the More A-More B intuitive rule and the impact of perceptual fluency on overcoming the interference of this rule among Chinese primary school students in a perimeter comparison task. Experiment 1 examined the characteristics and developmental patterns of the interference of the More A-More B intuitive rule among primary school students (Grades 3-6; N = 123) in a perimeter comparison task. The results demonstrated that Grade 3-6 students were interfered by the More A-More B intuitive rule while solving the task, especially among Grade 3 students. Experiments 2, 3, and 4 explored the influence of perceptual fluency on overcoming the interference of the More A-More B intuitive rule among Grade 3 students by using different experimental paradigms and different manipulation methods. A pilot experiment (Experiment 2; N = 40) was first conducted to test the validity of the manipulation of perceptual fluency. Experiment 3 (N = 70) used a between-subjects design to examine the impact of perceptual fluency on overcoming the interference of the More A-More B intuitive rule by manipulating the clarity of shapes. Controlling for individual differences, Experiment 4 (N = 27) used a within-subject design to further examine the impact of perceptual fluency on overcoming the interference of the More A-More B intuitive rule by presenting shapes either in a high figure-ground contrast or in a low figure-ground contrast. The results of Experiments 3 and 4 consistently showed that participants were significantly less interfered by the More A-More B intuitive rule under the lower perceptual fluency condition. In conclusion, these studies provide evidence for the effectiveness of a perceptual fluency manipulation to overcome the interference of the More A-More B intuitive rule.