Children's emotion word comprehension (EWC) has constantly received a great deal of attention in developmental science. However, since previous reports focused on only English emotion vocabulary, researchers thus far remained unclear as to the developmental trajectories of EWC (to Chinese emotion words) in Chinese children, let alone the cross-cultural difference of EWC in different languages (i.e., English V.S. Chinese). Furthermore, the influence of valence on EWC, as well as the interaction mechanism between EWC and empathy, has not been fully investigated. Finding answers to these research gaps has become the main motivation of the current study. For this purpose, a Chinese emotion vocabulary was first constructed to estimate EWC of Chinese children (ages 2-13 years old). Then, the valence of each emotion word was evaluated using the standard 9-point scale approach. After that, the Chinese children's EWC and empathy were measured in terms of parental ratings. Finally, all data collected were statistically analyzed to reveal the influence of the valence of EWC, the relation between EWC and empathy, and the cross-cultural difference of children's EWC between China and UK from the viewpoint of developmental science. The main results of the current study included the following: (i) EWC in general increased with age for Chinese children ages 2-13 years old, however, there was a dramatic increase during ages 6-8 years old; (ii) EWC of positive emotion words in general developed better than that of negative and neutral ones for Chinese children (ages 2-13 years old); and the disadvantage of EWC to negative emotion words over neutral ones was gradually observed with the increase of age, even though there were no significant differences between them from the beginning; (iii) EWC completely mediated the effect of age on empathy; and (iv) EWC of children in UK developed better than Chinese counterparts during the early childhood period (ages 4-6 years old), then Chinese counterparts developed better during the middle childhood period (ages 7-10 years old), however, there was no significant difference of EWC between both groups during the late childhood period (ages 11-12 years old).