The invention provides a separation method and device for mixed liquid, and belongs to the technical field of separation of two kinds of liquid. The separation method of mixed liquid comprises the following steps that S1, the mixed liquid which is insoluble mutually is layered, and the layered liquid is set to be liquid A and liquid B; S2, an interface recognizer of which the density is between the liquid A and the liquid B is prepared, wherein the interface recognizer can be prepared from one or more kinds of compound materials; and S3, the interface recognizer is put into the mixed liquid, and according to the own density characteristic of the interface recognizer, the interface recognizer can automatically suspend between the interface of the liquid A and the interface of the liquid B for accurately separating the liquid A from the liquid B in the mixed liquid. The separation method disclosed by the invention can be used for the separation of the mixed liquid which has a density contrast and is insoluble mutually; and through the adoption of the interface recognizer of which the density is between the mixed liquid, the content of the liquid at the lower layer in the pretreated mixed liquid can be accurately recognized.