This study investigated the status of equity in mathematics education in Hong Kong based on data from TIMSS 2011 to 2019 and the changes in education equity across the three cycles. The effects of various student-, family-, and school-level variables on students' mathematics achievement were examined and compared using multilevel modeling. Results showed that there were significant variances between schools in mathematics achievement in Hong Kong, especially for eighth grade students. Overall, boys performed better in mathematics than girls in these three TIMSS cycles in Hong Kong, except for eighth grade boys in the cycles of 2011 and 2019. The family and school socio-economic status (SES) related to the possession of traditional materials (e.g., desks and books) and parents' highest education level had positive and significant effects on students' mathematics achievement, and the effects of the predictors increased from the 2011 cycle to the 2019 cycle. SES related to the possession of home digital devices (e.g., computers and internet connection) also had positive but much less substantial effects. School location and resource availability did not have significant effects. In general, the mean levels of SES and school resource availability in Hong Kong is improving. However, the effects of some important student- and school-level factors on mathematics achievement increased. Suggestions for improving education equity in Hong Kong are discussed.