Introduction: the development of new drugs is a strategic goal of the pharmaceutical industry. New drugs and dosage forms are being created to treat various diseases. An important direction is the development of dosage forms with photoprotective properties based on fluorouracil. Purpose: composition, production technology, quantitative determination methods and explain the pharmacological action of a soft dosage form based on fluorouracil with nanoparticles. Materials and methods: we used 5-fluorouracil produced by Nantong Jinghua Pharmaceutical Co. Ltd. Quantification was performed using high-performance liquid chromatography HPLC (Shimadzu Corporation, Kyoto, Japan). To obtain nanoparticles, a gas-phase synthesis installation using induction-levitation melting was used. Results: The synthesis of nanoparticles has been carried out. A dosage form was obtained containing fluorouracil with nanoparticles as the active substance; polyethylene glycol (PEG) with different molecular weights was taken as the basis. General composition of the dosage form: Fluorouracil – 5 g (5%), delivery systems with magnetic response. Fe3O4 nanoparticles - 0.100 g (0.1%), nanoparticle size 40 nm. Excipients PEG 400 – 59.13 g, PEG 1000 – 24.4 g, Sodium hydroxide 1.37 g, Water 10 ml. A hardware scheme for producing ointments is proposed. Chromatography conditions have been developed. The method was validated, in which the indicators of linearity and accuracy of the method were determined, and metrological characteristics for the determination of fluorouracil in soft dosage form were carried out. The magnetic properties of Fe3O4 iron nanoparticles were determined using the Faraday method. A model of the action of a dosage form with nanoparticles is proposed. Conclusion: A composition of a soft dosage form based on fluorouracil with nanoparticles has been proposed. The production technology, quantitative determination method are developed in detail, and the pharmacological properties are explained.