The main purpose of this study was to explore the developmental changes of speech discrimination abilities in Mandarin-speaking children across preschool and school ages. This study also examined the relationship between speech perception abilities and word comprehension in childhood. 150 Mandarin-speaking 4-8 year-old children (30 for each age group) participated in AX phonetic discrimination tasks constructed by three phonetic contrasts with different speech acoustic features (i.e., stops with different articulation places, affricate vs. fricative, lexical tone 2 vs. 3) . The Peabody Picture Vocabulary Test (PPVT) was used to assess children’s word comprehension ability. The results that older children performed better speech discrimination and perceptual sensitivity than the younger ones on all three phonetic discrimination tasks indicated the progress of speech perception abilities during 4-8 years of age. In examining the phonetic contrast effects on the speech perception abilities, the results showed that children performed better on the lexical tone sensitivities than the affricate vs. fricative discrimination. In addition, the phonetic discrimination performance was positively correlated with the PPVT score, and the regression model showed that both lexical tone and stop consonant sensitivity contributed to the variance of PPVT scores, especially the lexical tone sensitivity contribute to word comprehension more than the stop consonant sensitivity. These results showed the improving sensitivity in discriminating native phonetic contrasts in 4-8 year-old children, and suggested that speech perception plays an essential role in word comprehension development in Mandarin-speaking children.