With the rapid growth in population and economic and social development, China's ecological and environmental damage incidents occur frequently, resulting in varying degrees of impact and damage to the structure and function of different ecosystems, which seriously threatens the safety of human life and property, natural resources and the health of ecosystem. Along with the successive releases of related technical guides and documents in recent years, identification and assessment of eco-environmental damage in China have been gradually developing towards professionalism, proceduralization and standardization, and the research on the related mechanisms and technical methods has been developing more and more sophisticated. Identification and assessment of eco-environmental damage refers to the process in which identification agencies conduct a scientific and reasonable analysis of the causal relationship between behavior of environmental damage and environmental damage, assess the scope and extent of environmental damage, and quantify the amount of ecological environmental damage. Systematic research on the theory and technical methods of identification and assessment of eco-environmental damage has important theoretical and practical significance for ensuring our country's ecological security and realizing regional sustainable development, and it is also an important aspect of promoting construction of China's ecological civilization. Grassland is the largest ecosystem in our country and the core area for construction of ecological civilization. However, grassland eco-environmental damage occurs frequently in recent years, it is necessary to formulate identification and assessment techniques and methods based on mechanisms and characteristics of the grassland eco-environmental damage. The judgement of causality is an important part of the identification and assessment of eco-environmental damage of grassland, and it is directly related to the accountability of eco-environmental damage of grassland. However, there are not many studies on the causality judgement of eco-environmental damage of grassland, and relevant systems need to be established as soon as possible to promote the further development of identification and assessment of eco-environmental damage of grassland. This article targets grassland eco-environmental damage and discusses one of its important processes of identification and assessment——causality judgement. The article puts forward the general process and basic logic of the causality judgement, which includes analysis of possibility of damage occurrence, identification of damage behavior, deduction of damage path, analysis of possibility of existence of other damage behavior and explanation of uncertainty, as well as judgement rules and theoretical basis. We hope to provide scientific basis for related work and policy makers of identification and assessment of the grassland eco-environmental damage.