This study aims to explore the relationship between family socioeconomic status and learning achievements of ninth grades in Penghu county, and used self-regulated learning and Chinese language achievement as mederators. Data were collected through questionnaires from 636 ninth graders, and results showed that (1) students had good self-regulated learning, situational adjustments, meta-cognition, cognitive strategies, and behavioral control were higher than the averagely standard; the Chinese language achievement and math achievement reached the basic level respectively; (2) the higher the family SES, the better self-regulated learning and learning achievements; girls’ self-regulated learning were higher than boys, and there was no significant difference between urban and remote areas students’ learning achievement and self-regulated learning; (3) in the relationship between family SES’s impacted on math achievement through self-regulated learning, self-regulated learning and Chinese language achievement had partially mediating effects; (4) in the relationship between family SES and mathematics achievement through self-regulated learning, these two mederators had partially mederated effects; (5) the best way to enhance math achievement was through the improvement of Chinese language achievement, followed by self-regulated learning and the improvement of Chinese language achievement, and finally through self-regulated learning.