Atpresentabout60%ofecosystemhasbeendamagedanddegradedseverely,resultinginenormousecologicallossglobally.Theessentialcauseistheirrationalutilizationofecosystembyhumankind,soitisthekeytochangingimproperenvironmentalperformanceofhumankindsoastopreventecosystemfrombeingdamaged.Thequantitativevaluationonthelossofecologicaldamageisaneffectivetooltoguidehumanecoenvironmentalperformance.Inthispaper,theconceptsrelatedtothevaluationonecologicaldamagecostareintroduced;uncertaintiesthatmightariseinthevaluationonthelossofecologicaldamagesuchasareacoverageofvaluation,ecologicaldamagequantity,bordersofecologicaldamagecostanddatasupportareanalyzed;andthevaluationapproachesforthelossofecologicaldamagearealsodiscussed.Asacasestudy,theeconomiclossesofecologicaldamageofforestin2005inChinaarevaluated.