Researchers are paying increasing attention to employee well-being with the prosperity of positive organizational behavior. This study aims to investigate how employee well-being levels vary according to the demographic factors and the job characteristic factors. Moreover, it explores the mechanism through which job-related stress affects employee well-being. By conducting questionnaire survey in Beijing, Shanghai, Nanjing, Chengdu, Changsha and Guangzhou, the authors obtained a sample of 305 Chinese mainland employees. 266 questionnaires are valid. The questionnaire comprises three parts. Part one includes items asking the demographic characteristics and the job characteristics of respondents. Part two adopts the Subjective Well-being Scales developed by Diener, including the Life Satisfaction Scale and the PA-NA Scale. Part three adopts the scale developed by House et al and measures the job-related stress of employees. This part including Job Responsibility, Job Quality, Role Conflict, Work and Non-work Conflict, and Overload. All measures altogether include 15 items . The results are as following. First, employees generally experience relatively low levels of life satisfaction and positive affect, and often have negative affect. Second, employees differ significantly in negative affect according to the age and education level. With regard to age, the employees under 25 and those between 36 and 40 have significantly higher negative affect than counterparts between 26 and 30. Regarding the education level, employees with college degree experience significantly higher negative affect than those with university degree or above. Meanwhile, employees with postgraduate degree or above have significantly lower negative affect than counterparts with university degree. Third, employees from different ownership companies differ significantly in life satisfaction. Employees from private enterprises have significantly lower life satisfaction than those from state-owned enterprises or joint-equity enterprises. Fourth, employees from different positions differ significantly in negative affect. Salesmen have far more negative affect than managers and research personnel. Fifth, employees from different industries have different levels of positive affect. Employees from trade industry have significantly higher positive affect than those from high-tech industry or from manufacturing industry. People from service industry have higher positive affect than those fro