The HIV epidemic continues to develop among older adults in China, including older female sex workers. Yet, few studies have been conducted among this relatively hidden population. The objectives of this study were to investigate the reasons for women's entry into sex work during their 30s and to develop typology of older women sex workers. Semi-structured in-depth interviews were conducted with 63 older women sex workers and six focus-group interviews with stakeholders in three cities in China in 2012. Data were analysed inductively using constant comparative method. The mean age of participants was 43 years and the mean age of entry into sex work was 39 years. The primary reasons for entry into sex work included heavy economic burdens, limited employment opportunities and the appealing nature of sex work. Street-based and venue-based older sex workers were identified based on where they solicited clients. Street-based older sex workers were more likely to engage in unsafe commercial sex due to financial incentives, whereas those in entertainment venues were unlikely to use condoms with regular clients. The development of effective HIV interventions needs to consider older women sex worker's unique characteristics and target factors that impede safer-sex practices.