Objective To calculate the unit cost of interventions for commercial sex workers (CSW) by applying health economics aproaches through investigating the contents and expenditures of interventions in districts A and B of X City with low HIV/AIDS prevalence. Methods The contents and unit price of interventions were analyzed through direct inquiry and data review. A descriptive analysis of the data obtained was developed to calculate the u-nit cost by using the "Costing Guideline for HIV/AIDS Intervention Strategies (ADB model)". Results In 2010, the unit cost of CSW interventions in districts A and B was RMB 98. 46 and 68. 07 yuan per person per year. In districts A and B, the intervention expenditures were mainly used for outreach activities, peer education, condom use and information education and communication (IEC). Conclusions The contents, frequency and unit prize of interventions and size of the target population are all important factors influencing the unit cost of CSW interventions.