The invention relates to a system and a method for evaluating influence of direct current bias in a mountainous area environment. The evaluation system comprises a mountainous area model building module, an evaluation model building module and an evaluation result acquisition module, wherein the mountainous area model building module is used for establishing a mountainous area environment model which conforms to the actual environment; the evaluation model building module is sued for adding a power grid topology model to the mountainous area environment model to form a complete evaluation model; and the evaluation result acquisition module is used for acquiring and outputting an influence result of direct current bias in the mountainous area environment. Compared with the prior art, the system and the method have the advantages of high accuracy, suitability for complicated environment and the like.