The application provides an isolator comprising a main member; the main member comprises two sets of magnet arrays, a Faraday optical rotation assembly and two first magnetic line guiding blocks; the Faraday optical rotation assembly comprises a Faraday member; a medial axis is installed between the two sets of magnet arrays; the two sets of magnet arrays are symmetrically distributed around the medial axis; the magnet arrays comprise a first part, wherein the first part is a part where a magnetic line of force is parallel to the medial axis; the Faraday member is positioned between the first part of the two sets of magnet arrays; two first magnetic line guiding blocks are positioned between the two sets of magnet arrays and positioned at two ends of the Faraday member. According to the application, the first magnetic line guiding blocks are used for receiving openly spread magnetic line of force to increase the utilization rate of a magnetic field and the magnetic field intensity in the Faraday member so that larger optical rotation angle is obtained. The size of Faraday members of isolators can be further reduced and cost is reduced.