Background The Family Doctor Contract Service (FDCS) system is a service model for primary care reform launched in 2016 to offer families and individuals active and continuous health care by a team of family doctors within primary care institutions in China. Objectives This study aimed to estimate socioeconomic-related inequalities in the utilization of basic public health services, and to identify the contribution of FDCS to promoting equality. Methods Data for the study were collected from a 2023 cross-sectional household health survey in western China, involving 39,456 participants. The concentration index (C) was employed for analyzing the extent of socioeconomic-related inequalities in the utilization of basic public health services and the coarsened exact matching technique was employed for sensitivity analysis in order to reduce selection bias. Results Our results indicated pro-poor inequalities in the utilization of health records (C = -0.046), free health check-ups (C = -0.009), and follow-ups for hypertension (C = -0.051). Additionally, a more equitable distribution across the economic spectrum was observed within the FDCS group (people who voluntarily contracted for services) compared to the non-FDCS group. The FDCS demonstrated more favorable positive impacts among individuals with higher (quintiles 60-80%) and the highest (top 20%) socioeconomic status. The FDCS contributed 83.94%, 59.24%, and 36.92% to pro-poor inequalities in the utilization of three basic public health services. These contributions reflected the positive impact of the FDCS on utilization. Conclusions Government policy and service delivery models require a paradigm shift to promote a stronger primary healthcare approach to practice, as evidenced by the effectiveness of the FDCS in promoting equality.