Abstract: What is an appropriate sample size? How does sample size influence the quality of empirical research? These are the preoccupations that empirical researchers generally have in the process of research design and evaluation. The 105 articles (including 111 experiments) published in 4 representative sport scientific journals in Chinese are analyzed and several existing problems on sample size are spotted. It aims to discuss the influence of sample size on statistical power, type Ⅰ error, effect size estimation and research replicability. Furthermore, multiple ways are introduced to estimate a proper sample size for empirical studies in sport science, which includes rules based on hypothesis, research types, research designs and sample availability. Apart from these, researchers are also advised to report and verify the planned and actual sample sizes in empirical research during the phases of research proposal and manuscript submission.