The invention relates to the field of slow-release material application, and discloses a preparation method of a green long-acting portable solid fragrance agent. The method comprises the following steps: S1, crushing and drying colloid-grade attapulgite; S2, uniformly mixing the treated colloid-grade attapulgite and essential oil according to a certain proportion to prepare a high-concentration raw material, and uniformly mixing according to another proportion to prepare a low-concentration raw material; S3, pressing the high-concentration raw material into pills at constant pressure; and S4, taking the pills serve as inner cores, placing the low-concentration raw material into the pills to serve as outer shells, ensuring that the inner cores are evenly wrapped in the outer shells, then performing secondary pressing under the constant pressure, and preparing the green long-acting portable solid fragrance agent of the core-shell structure. According to the method, the use of organic auxiliary reagents is completely eradicated, fragrance diffusion equipment assistance is not needed, the fragrance release rate can be adjusted, the long-acting slow release is effectively ensured, the preparation process is simple, the cost is low, the use is green and pollution-free, the essential oil utilization degree is high, the residual oil rate is low, and the VOC pollution is avoided.