A method for the preparation of cannabinoid acids having general formula (I, II, III, IV), wherein R1 = linear or branched alkyl group, alkenyl group or alkynyl group having from 1 to 5 carbons; wherein the method includes the following steps: a) immersing plant material of the Cannabis sp plant containing substances of formula I or II or III or IV with R1 = H in alcohol, straight or branched and with a number of carbon atoms from 1 to 5, in a ratio of dry plant material: alcohol from 1:10 to 1: 100; b) adding 4-dimethylaminopyridine (DMAP) to the mixture, in a ratio of mol DMAP: mol of cannabinoid acids from 1:10 to 1: 1; c) adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to the mixture, in a ratio of 2 mol EDC: 1 mol of cannabinoid acids; d) placing the mixture in an ultrasonic bath for 15 to 45 minutes; e) filtering the mixture to remove plant material; f) adding an acid solution to the alcoholic solution obtained from step e; g) performing a liquid-liquid extraction with an organic solvent immiscible with the alcohol-water mixture obtained from step f; h) washing the organic solvent with an aqueous alkaline solution and water; and i) evaporating the organic solvent to dryness to obtain the cannabinoid acid esters of formula I or II or III or IV, with R1 = straight or branched alkyl group, alkenyl group or alkynyl group having from 1 to 5 carbons. R1 = linear or branched alkyl group, alkenyl group or alkynyl group having from 1 to 5 carbons; wherein the method includes the following steps: a) immersing plant material of the Cannabis sp plant containing substances of formula I or II or III or IV with R1 = H in alcohol, straight or branched and with a number of carbon atoms from 1 to 5, in a ratio of dry plant material: alcohol from 1:10 to 1: 100; b) adding 4-dimethylaminopyridine (DMAP) to the mixture, in a ratio of mol DMAP: mol of cannabinoid acids from 1:10 to 1: 1; c) adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to the mixture, in a ratio of 2 mol EDC: 1 mol of cannabinoid acids; d) placing the mixture in an ultrasonic bath for 15 to 45 minutes; e) filtering the mixture to remove plant material; f) adding an acid solution to the alcoholic solution obtained from step e; g) performing a liquid-liquid extraction with an organic solvent immiscible with the alcohol-water mixture obtained from step f; h) washing the organic solvent with an aqueous alkaline solution and water; and i) evaporating the organic solvent to dryness to obtain the cannabinoid acid esters of formula I or II or III or IV, with R1 = straight or branched alkyl group, alkenyl group or alkynyl group having from 1 to 5 carbons. a) immersing plant material of the Cannabis sp plant containing substances of formula I or II or III or IV with R1 = H in alcohol, straight or branched and with a number of carbon atoms from 1 to 5, in a ratio of dry plant material: alcohol from 1:10 to 1: 100; b) adding 4-dimethylaminopyridine (DMAP) to the mixture, in a ratio of mol DMAP: mol of cannabinoid acids from 1:10 to 1: 1; c) adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to the mixture, in a ratio of 2 mol EDC: 1 mol of cannabinoid acids; d) placing the mixture in an ultrasonic bath for 15 to 45 minutes; e) filtering the mixture to remove plant material; f) adding an acid solution to the alcoholic solution obtained from step e; g) performing a liquid-liquid extraction with an organic solvent immiscible with the alcohol-water mixture obtained from step f; h) washing the organic solvent with an aqueous alkaline solution and water; and i) evaporating the organic solvent to dryness to obtain the cannabinoid acid esters of formula I or II or III or IV, with R1 = straight or branched alkyl group, alkenyl group or alkynyl group having from 1 to 5 carbons.