Abstract: Project risk assessment for urban drainage monitoring system could increase the capacity to resist project risk and promote project popularization of wastewater on-line monitoring system. After the analysis of related risk impact factors, a risk assessment index system based on field surveys and expert questionnaire in Guangzhou is established by using grey evaluation method i.e. grey decision method and grey relational analysis method. Some conclusions have been drawn. They are as follows: There are a lot of risks in entire project life cycle of auto-monitoring system for urban wastewater. And the risk existing in construction phase is bigger than that in other phases. Among these risk indicators in the project life cycle, some indicators have relatively high weights, such as the feasibility demonstration, the reasonability for collecting water samples, the maintenance and expansion of equipments, the monitoring data quality, and the quality of employees, et al. If the more attention to is paid these indicators, the risks could be reduced.

Key words: auto-monitoring system, project risk assessment, grey evaluation, wastewater on-line monitor