For the case that supply is less than demand (Case $ S $) or supply is more than demand (Case $ G $) within a time period in service sharing, the optimal pricing and service level decisions of two B2C service sharing platforms in the competitive environment are studied. First, the Nash game models of two platforms in each case are constructed, and the equilibrium results are obtained by solving the models, including service prices, service levels, actual demands and platform profits. Further, the effect of the number of shared products on the equilibrium results under different cases is analyzed. The research results show that if the total number of shared products launched by the two platforms is less than a threshold, the optimal service price and service level of a platform under Case $ S $ are greater than those of the platform under Case $ G $. If the total number of shared products launched by the two platforms meets certain conditions, the profit of a platform under Case $ S $ is greater than that of the platform under Case $ G $. The social welfare under Case $ S $ is greater than that under Case $ G $ when the average usage of shared products used by consumers is large.