Provided in the present invention are a new type indoleamine 2, 3-dioxygenase inhibitor and a preparation method and pharmaceutical composition thereof, wherein the definitions of the R and X groups are as shown in the description. Also provided are the use of the compound and a pharmaceutically acceptable salt and isomer thereof in the preparation of a drug for a disease associated with indoleamine 2, 3-dioxygenase (IDO), and in particular the use of the same in the treatment of multiple serious diseases such as cancers, Alzheimer' s disease, depression and cataracts. The compound of the present invention has good activity, and has potential medicinal value and broad market prospects.