According to the brand personality dimension theories and models, a brand positioning diagnosis method is established based on the brand personality dimensions. This method is used to measure the differences of brand personality between the ideal brand and a specific brand, identify consumer preferences for brand personality, and determine whether a specific brand can satisfy consumer preferences. Then we evaluate the deviation degree of brand positioning combined with the market performance of the specific brand. An Empirical Analysis of children's wear brand is conducted to prove the effectiveness of the method, and some advices in children's wear brand positioning strategy are presented.