The invention belongs to the technical field of preparation of micro-nano fibers, and relates to a preparation method of a micro-nano fiber with an annular structure. The preparation method comprises the following steps of firstly, preparing an electrostatic spinning solution, and loading the prepared electrostatic spinning solution into a spinning solution container, wherein the area of a metal collection device with adjustable adjusting area is 9-15mm2, and the distance between a spinning spray head and a glass sheet is 5-20cm; then, opening a high-pressure electrostatic generator, adjusting the voltage to 10-40kV, performing the electrostatic spinning for 10-30s, and closing the high-pressure electrostatic generator, so as to obtain the micro-nano fiber with the annular structure. The preparation method has the advantages that the preparation process is simple, the structure of the adopted device is simple, the distribution of electric fields in the preparation process is centralized, the easiness in loss of charges is avoided, the action of internal repelling is continuously performed, and the prepared micro-nano fiber with the annular structure has the positive promotion function on broadening the application range of the electrostatic spinning fiber.