Background: Although the standing long jump (SLJ) is a popular physical fitness assessment, it lacks an updated criterion-reference standard. This study generated the first normative SLJ test data for Chinese aged 8 - 18. Methods: From September 2005 to December 2011, comprehensive physical fitness assessments were conducted on 12,712 school students. The SLJ performances were significantly different between boys and girls (all age groups, p < 0.01). Results: The boys performed better than the girls in each age group. The mean difference increased as the age increased, depicting a prominent variance in muscular strength between boys and girls at age 12, and the variances became larger at age 18. Girls in the 70th percenttile performed similarly to boys performing in the 10th percentile. The onset of muscle strength for boys found in this study corresponded to the onset age of testosterone maturation of Chinese boys investigated in previous studies. Linear regression found age and BMI predicting SLJ significantly for boys and girls, explaining better SLJ results in older boy and the effect of their heavy body size. Conclusions: This study indicated a muscular strength difference between genders during growth and added supporting evidence to the hormonal influence of muscle growth during puberty.