The invention discloses a magnetic field demonstrating method and a device based on a magnetic fluid and a mixing reality technology, wherein the method comprises the following steps: s1. Shooting animage displayed by a magnetic fluid demonstrator; S2. Identifying the peaks of the mountain structure in the image and calculating the number of peaks and the height of each peak; S3. Assigning magnetic induction lines to the magnetic field strength of each mountain peak region so that the number of magnetic induction lines in the region as a proportion of the total number of magnetic induction lines coincides with the height of the mountain peak as a proportion of the total height of the mountain peak; S4. Superimposing the magnetic induction line and the original image, and performing demonstration through a display; The device comprises a magnetic fluid demonstrator, a small depth-of-field camera, an upper computer and a display; The invention realizes the visual display of the magneticfield distribution combined with the phase change form of the magnetic liquid by using the mixed reality technology, so as to realize the good demonstration of the magnetic field distribution.