This study aims at developing and testing a pragmatic expert system for HIV voluntary counseling (VCT-ES) that leverages best practices. The VCT-ES was developed via evolutionary prototyping and piloted in 10 voluntary HIV counseling and testing (VCT) clinics from Anhui and Beijing representative of prefecture and county level VCT clinics in China. All counselors with the clinics and the clients to the clinics within selected two weeks at baseline and the end of study were invited to participate. Assessment measures included essential counseling procedures (ECPs); clients' satisfaction, knowledge, and behavior efficacy. VCT-ES was developed which tries to model and facilitate standard VCT operation procedures and best practices. One hundred and eighty-two (96 at baseline vs. 86 after intervention) cases recordings, 172 (96 vs. 76) client questionnaires, 10 counselor, and 2 expert rating instruments were collected; and 17 clients and 8 counselors participated in qualitative interviews. VCT-ES increased delivery of ECPs from 18.94% to 66.39% on average; increased clients' knowledge from 40.51% to 86.34% and self-efficacy by 22.42%. The VCT-ES applications listed were rated 9.1 on average (maximum = 10). The VCT-ES could be an easy and effective solution to better routine VCT and merits further research.