Purpose The aim is to examine the effects of social networks characteristics of drug addicts in MMT clinics, to promote HIV/AIDS spread control.

Method In the first stage targeted sampling method will be used, 144 patients will be sampled in outpatient in MMT clinics. In the second stage 20 people drawn from the 144 patients will be randomly sampled and the social network nomination method employed with investigating individual network nomination.

Results The proportion of female drug addicts has increased over the past 10 years. The average length of drug injection history is 12.68 years. Surveys show that HIV infections among this group are more frequently increasing in Yunnan than in other provinces of China. The proportion of single people differs from that of the married people (X2 = 9.242, P < 0.017). The syringe reuse, syringe cleaning and needle sharing are statistically significant to the infection with HIV (P < 0.01). The “key persons” characteristic of the social network, have a certain influence over the network members. The centre network analysis of 22 individuals indicated that the maximum network size of individual drug use group members was 6 persons, and the minimum network size was 3 persons.

Conclusion For the prevention of risky behaviours in the high-risk groups, the past experience from other countries should be taken into account. Cutting off the transmission ways is regarded as leading method, but should be combined with comprehensive prevention measures. It is necessary to build good social atmosphere for the control of the spread of HIV/AIDS, to improve the social communication network for the receivers of methadone maintenance treatment, and to extend the network of formal social support groups in order to improve availability of health services information for receivers of methadone MMT, to promote the recovery of social functioning, and to increase social participation of MMT receivers.