Marine ecosystem health assessment is an integrated process to solve complexity in marine ecosystem with systematical, flowing, hierarchy and complex characteristics. Up to now, it is difficult to determine the relationship between the complexity and the health of marine ecosystem because of ecosystem diversity. There are a lot of problems of ecosystem complexity in the assessment mainly including: (1) The characteristics and uncertainty of marine ecosystem are the important presupposition to definition and interpret the connotation of ecosystem health; (2) Generally speaking,  ecosystem health assessment includes biophysical, socioeconomic, human health, social policy and spatial-temporal scales; (3) The elements of assessment refer to biological, physical, chemical and social-economical factors; (4)Assessment units and standards determination; (5)Assessment methods divides into two kinds of indicator species and structural-functional indicators by analysing methods of AHP, DEA, fuzzy evaluation and grey correlation analysis; (6) The construction of assessment indicators is a of complex and difficult work. The indicators consist of not only vigor, organization and resilience but also the indicators of keeping ecosystem services, selecting management carrying, outside input, impacts on nearby ecosystem and human health; (7) It should be constructed by Driving forces-Pressure-Status-Response-Control model(D-PSR-C model) to assessment marine ecosystem health; (8) The results should be comprehensively analysed in order to establish measurements for ecosystem management with the main tasks of exactly distinguish pressures by human kinds or natural disturbance, which are one of the standards to select efficient assessment indicators.

Keywords: Marine ecosystem, Health assessment, Ecological Complexity, Indicator system, Integrated Assessment model

Note: Oral presentation in EcoSummit 2007：Ecological Complexity and Sustainable Development: Chanllenges and Opportunities for 21st Centuary