To improve libraries’ reference services under Web 2.0,we borrow ideas from community-based question answering(Q&A) services on the Web,and compare them with library joint reference services based on service features,reference contents and customization features.Our study also includes asking questions directly at both the community-based Q&A sites and the reference services and evaluates them based on answer quality and the efficiency.The questions are classified into factoid questions,enumerative questions,and definition questions,covering topics in economics,literature and library science.Results show that community-based Q&A sites provide more answers with shorter response time while reference services are better at answering factoid questions:Joint reference services should learn from community-based Q&A sites about their flexible service features and effective question answering methods.It is also worth promoting the service-concept in IPL2 to other reference services.