Despite increased investment in rural education in recent years, the academic achievement of ethnic minority students in rural China continues to lag behind their Han Chinese peers. Few studies have used up-to-date data to measure the size of this achievement gap, and none have examined whether differential math attitudes and math anxiety play a role in perpetuating it. Using data from a survey of 16,747 students in 235 rural primary schools, we find a significant disparity in math performance between ethnic minority and Han students, with minority students scoring 0.25 standard deviations lower than their Han peers. Multivariate analysis reveals that differences in math affinity and math anxiety were significantly associated with math achievement among ethnic minority and Han students. Decomposition analysis further reveals that up to 37% of the achievement gap can be explained by variations in student, parent, and teacher characteristics. The difference in household asset was the largest explained contributor to the Han-minority achievement gap, followed by math affinity and math anxiety. This study underscores the importance of addressing students' math affinity and math anxiety in narrowing rural achievement gaps and promoting equitable educational outcomes in rural China and abroad.