In the process of sexual selection in animals, larger individuals typically occupy higher hierarchical positions, dominate more resources, and have higher offspring survival rates and better genes compared to smaller individuals. Thus, they may be preferentially selected by the opposite sex. Activity, as one of the important personality traits, has been shown to be related to offspring health and may serve as another important criterion for selection apart from size. However, it is still unclear how personality traits influence sexual selection in fish, given the complex nature of these traits and their interactions. Additionally, the impact of personality traits on same-sex individual preferences in fish has also been long overlooked, despite its potential significance in understanding social dynamics and mating systems within fish populations. To investigate whether the personality affect fish preferences for different-sized or active individuals (both of the same and opposite sex), this study examined the behavioral preferences of rose bitterlings (Rhodeus ocellatus) during the breeding season and measured their activity, boldness, and aggression as personality traits. Based on these results, the associations between behavioral preferences and personality traits were analyzed. The results showed that (1) activity, boldness, and aggression were positively correlated, and female fish were significantly braver and more aggressive than male fish; (2) female fish showed a clear preference for larger and more active male individuals, but the preference was not statistically significant. In contrast, male fish preferred smaller female individuals; (3) brave and aggressive female rose bitterlings had a greater preference for larger or more active individuals of the same or opposite sex. However, none of the personality traits in male fish were related to their behavioral preferences for both the same and opposite sex. The preference of female fish for larger or more active male individuals may improve the survival rate and competitive ability of their offspring, while the preference of male fish for smaller female individuals may be related to the greater aggression of female fish. Additionally, the behavioral preference of female fish for both same-sex and opposite-sex individuals was consistent with the "behavioral similarity" principle, which suggests that individuals tend to choose partners with similar personalities. This similarity can facilitate coordination in reproductive activities with partners and cooperation with same-sex peers in daily activities, enhancing overall group cohesion and success. Understanding these dynamics is crucial for comprehending the broader implications of personality traits on social and reproductive behaviors in fish populations, shedding light on the evolutionary pressures shaping these traits.