The invention provides a porous graphene oxide and a preparation method thereof, a porous graphene oxide coated slow-release chemical fertilizer and a preparation method of the chemical fertilizer, and relates to the field of chemical fertilizer. The preparation method of the porous graphene oxide coated slow-release chemical fertilizer comprises the steps: mixing a chemical fertilizer and porousgraphene oxide with the weight ratio of (5-2000):1, adjusting the pH to 11-12, and then stirring for 1-5 h at room temperature; and mixing and stirring a third mixed solution and plant oil for 0.5-5 hwith the weight ratio of 1:(3-10) at a temperature of 85-95 DEG C to obtain a fourth mixed solution, and followed by centrifuging, filtering and washing until the plant oil is removed. The preparation method is simple, convenient and highly operable. Microsphere contents of the prepared porous graphene oxide coated slow-release chemical fertilizer are easy to diffuse, and a coating film has strong hydrophilicity, so the chemical fertilizer inside the microspheres is advantageously diffused to soil, and a chemical fertilizer diffusion path is short. At the same time, the chemical fertilizer has extremely strong compatibility with the environment, and also can play a role in fixing carbon in soil.