Few quantitative models can be found amenable to the quantitative evaluation of social work, which motivates the presented work. Moreover, a few related existing works suffer from no suitable indicator system and high expenses of time and money. To overcome these limitations, a real-time quantitative evaluation model using the Internet open-source big data was developed, a target indicator system was established, the rapid computation methods of each criterion were proposed, and a prototypical software system was designed and implemented. Case studies on selected social work were conducted, and the work performance of the 14 cities belonging to a certain province in China was evaluated. Results achieved were largely consistent with the subjective feelings of many respondents and relevant official assessment, which validated the efficiency and rationality of the proposed model.