The invention provides a preparation method of paramagnetism phenolic aldehyde polymer composite microspheres. The preparation method comprises the following steps: mixing a water-soluble phenol solution, a water-soluble aldehyde solution, a catalyst, a water-based magnetic fluid and a water-phase solvent so as to obtain a water phase; mixing a surfactant with an oil-phase solvent, dropping the water phase, and performing emulsification so as to obtain an emulsion; and performing a polymerization reaction on the emulsion, so as to obtain the paramagnetism phenolic aldehyde polymer composite microspheres. According to the preparation method, a mixed solution of the water-soluble phenol solution, the water-soluble aldehyde solution and the water-soluble magnetic fluid is subjected to inverseemulsion polymerization under a condition of an alkali catalyst, and the paramagnetism phenolic aldehyde polymer composite microspheres which are controllable in size and uniform in size distributionare prepared at one step. Due to adoption of water-soluble raw materials, the affinity of the raw materials with high-magnetism nanoparticles can be improved, and particularly phenolic hydroxyl groups in phenols of the raw materials and the magnetic nanoparticles form intensive hydrogen bonds, so that solid bonding can be achieved. The method provided by the invention is simple in magnetic nucleus preparation process, and prepared magnetic nuclei have the characteristics of being controllable in size, narrow in size distribution, rapid in magnetism response, simple and convenient in structuremodification, and the like.