This study examined the contributions of preschool language abilities and literacy activities arranged by teachers inside school to later reading achievement in students engaged in the fourth grade at primary schools. Data come from the Progress in International Reading Literacy Study (PIRLS) with Hong Kong samples across 2001 and 2006. 5,050 and 4,712 participants have taken part in PIRLS 2001 and 2006, respectively. Data were submitted to chi-square test, T-test and structural equation modeling to test the differences across samples, as well as find out the possible underlying mechanism between preschool language abilities, literacy activities and reading achievement. Results showed that: 1) students participated in PIRLS 2006 were significantly better prepared at language abilities at their entries to primary schools; 2) less literacy activities were assigned to students in 2006; 3) participants in PIRLS 2006 performed better in reading achievement than that in PIRLS 2001, significantly; 4) preschool language abilities are important in predicting later reading achievement in primary school; 5) effect of literacy activities arranged by teachers inside school would be strengthened when linking with preschool language abilities. Key Words: Preschool Language Abilities; Literacy Activities; Reading Achievement; PIRLS