This is an era that emphasizes individual expression and "who am I". Consumers pursue personalized expression and desire "self-congruence". On the one hand, customization provides an effective way for consumers' personalized expression. On the other hand, brand purchase also reflects the personality of consumers. Consumers show their brand purchases in front of the public, hoping that the public can accurately perceive their true types. When the brand public perception has a high degree of fit with its own personality, consumers will get a positive public perception effect. Otherwise, it will produce a negative public perception effect. We study how social sharing, public perception and product customization work together to affect consumers' personalized expression psychology and then affect consumers' purchase decisions and brand benefits. In this paper, we establish an economic model to investigate how social sharing and public perception affect brand customization decisions, and analyze what product strategies a brand should adopt at different stages of development and how to use social sharing and public perception effects to improve its own profits. Our analysis shows the value of brand customization, and obtains the optimal customization strategies for brands in two different stages. It is found that social sharing and public perception improve the profits of brands in the mature stage, while damaging the profits of brands in the initial stage. In other words, social sharing can further consolidate the development of brands in the mature stage. However, if the brand in the initial stage uses the traditional way to expand the social sharing effect, it will be detrimental to its own development. Our theoretical findings reveal how brands can satisfy consumers' personalized expression needs by providing customization and designing marketing strategies with the help of social media.