For the problem that NdFeB permanent magnet is brittle and has moulding difficulties in making micro structure，magnetorheological fluid was used as the actuated material for the micro magnetic robot，and a spherical robot for targeted drug delivery in human stomach was designed． According to the rheological principle of magnetorheological fluid，the mechanical relationship of magnetic particles in magnetic field was analyzed，and the dynamic model of spherical robot was established and simulated． The magnetic robot motion image acquisition system was built and robot displacement was calculated with Hough transform circle detection algorithm． Finally，a prototype robot was made and its motion characteristics were tested on an experimental platform with space magnetic field． Ｒesults show that the spherical actuated robot based on magnetorheological fluid is easy to control and its motion is stable and reliable.