Ergonomic consideration on workers in manufacturing work has been attracted attention by industries. Physical safety and mental stability, which would be offered to workers by a well-designed ergonomic work environment, could not only provide job satisfaction to the workers, but also could enhance productivity in manufacturing work. This study develops a prototype monitoring system of ergonomic working posture in a manufacturing work environment. The methodology of this monitoring system is based on the experimental observation using an experimental tool of X-box cameras controlled by XAMPP software to monitor the posture of workers. As for the ergonomic environment measurement, the system installs the five types of instrumental sensors, which include sound, light, temperature, vibration and indoor air quality. Capturing the body posture of subjects, the system measures the frequency of body bending, the angle of body bending and the time period of the same position kept by the body. Potentially useful several parameters are used in the experiments of this study. These parameters include temperature, light, vibration, body posture, indoor air quality and noise. The parameters are captured in analogue signals, which can be converted to digital signals by a signal converter. The analysis of worker posture on RULA (Right Upper Limb Assessment) was also conducted by using several software tools. Reviewing the experimental results using the monitoring system in a manufacturing industry at welding assembly section, this paper shows the feasibility of the proposed system.