Introduction: Social development problem of childrens social several years in increasing, especially in West Java year 2014 reaches 42% experienced social delay. The less social development can cause problems such as social hazards, psychology and self-conceptual disturbances. One of the efforts in improving social development is with bibliotherapy stimulus. The purpose to determine the influence of bibliotherapy on social development of preschool children in RA AL-Hidayah District Buahdua Sumedang District. Methods: The research methodology Pre Experiment with pualest-postest without control group design. Sampling using consecutive sampling technique. The sample in this study were children aged 3-6 years as many as 17 respondents. The instruments used are 18 items of observation on the socialization of children which is a modification of VSMS, KPSP, DDST, and Hurlock (2014) theory. The statistical test used is the difference test of two dependent means (t dependent). Results: The results (p value = 0.002 <α = 0.05) showed there influence of bibliotherapy on the social development of preschoolers. Conclusions: Based on research results suggested RA AL-Hidayah make bibliotherapy as one of the school program in an effort to improve social development of children.