There are more and more methods for the assessment of river health at present，but many methods rely too much on expert advice,which can't reflect the situation of river health objectively and accurately.In order to eliminate the errors due to human subjective evaluation,This paper attempted to combine the projection pursuit cluster and extenics muster theory to propose a new model of river health evaluation which based on projection pursuit-extension set theory. The paper used this model to evaluate the health of Huzhou in Taihu River basin for sequence of four years.The results show that the river health of Huzhou city is at a “very healthy”(Class I) level in 1991, and “healthy”(Class Ⅱ )level in 2001, the river health continued to deteriorate in 2006 and 2010 which is at “sick”(Class V)level.By comparing the same objective evaluation method of entropy weight matter-element model,The result is in fully consistent with evaluation findings.Projection pursuit-Extension set theory overcome the subjectivity of evaluation process to the greatest extent possible,deeply analyzed and unearthed contribution degree size among data and information.The method provides a new way of thinking and method for the assessment of river health even in plain river basin.