A preparation method of (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof, which comprises the following reaction steps: 1) Taking 4-fluoro-3-methylphenol as the starting material, and brominating it at a reaction temperature of -78°C to -10°C for a reaction time of 1-5 h to obtain 2-bromo-4-fluoro-5-methylphenol; 2) Performing O-alkylation reaction between 2-bromo-4-fluoro-5-methylphenol and 2-bromo-1,1-diethoxyethane at a reaction temperature is 70-150°C for a reaction time of 1-20 h to obtain 1-bromo-2-(2,2-diethoxyethoxy)-5-fluoro-4-toluene; 3) Cyclizing 1-bromo-2-(2,2-diethoxyethoxy)-5-fluoro-4-toluene to obtain 7-bromo-5-fluoro-4-methylbenzofuran; 4) Brominating 7-bromo-5-fluoro-4-methylbenzofuran to obtain 7-bromo-4-(bromomethyl)-5-fluorobenzofuran; 5) Preparing (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof using the following two-step reaction in any one of 5.1 or 5.2: 5.1) Aziding 7-bromo-4-(bromomethyl)-5-fluorobenzofuran in the presence of an azide, at a reaction temperature of 20-80°C for a reaction time of 1-20 h, to obtain 7-bromo-5-fluoro-4-azidomethyl-benzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof; or 5.2) Ammonolyzing 7-bromo-4-(bromomethyl)-5-fluorobenzofuran, at a reaction temperature of -30-25°C for a reaction time of 1-48 h, to obtain 7-bromo-4-(aminomethyl)-5-fluorobenzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof. 1) Taking 4-fluoro-3-methylphenol as the starting material, and brominating it at a reaction temperature of -78°C to -10°C for a reaction time of 1-5 h to obtain 2-bromo-4-fluoro-5-methylphenol; 2) Performing O-alkylation reaction between 2-bromo-4-fluoro-5-methylphenol and 2-bromo-1,1-diethoxyethane at a reaction temperature is 70-150°C for a reaction time of 1-20 h to obtain 1-bromo-2-(2,2-diethoxyethoxy)-5-fluoro-4-toluene; 3) Cyclizing 1-bromo-2-(2,2-diethoxyethoxy)-5-fluoro-4-toluene to obtain 7-bromo-5-fluoro-4-methylbenzofuran; 4) Brominating 7-bromo-5-fluoro-4-methylbenzofuran to obtain 7-bromo-4-(bromomethyl)-5-fluorobenzofuran; 5) Preparing (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof using the following two-step reaction in any one of 5.1 or 5.2: 5.1) Aziding 7-bromo-4-(bromomethyl)-5-fluorobenzofuran in the presence of an azide, at a reaction temperature of 20-80°C for a reaction time of 1-20 h, to obtain 7-bromo-5-fluoro-4-azidomethyl-benzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof; or 5.2) Ammonolyzing 7-bromo-4-(bromomethyl)-5-fluorobenzofuran, at a reaction temperature of -30-25°C for a reaction time of 1-48 h, to obtain 7-bromo-4-(aminomethyl)-5-fluorobenzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof. 5.1) Aziding 7-bromo-4-(bromomethyl)-5-fluorobenzofuran in the presence of an azide, at a reaction temperature of 20-80°C for a reaction time of 1-20 h, to obtain 7-bromo-5-fluoro-4-azidomethyl-benzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof; or 5.2) Ammonolyzing 7-bromo-4-(bromomethyl)-5-fluorobenzofuran, at a reaction temperature of -30-25°C for a reaction time of 1-48 h, to obtain 7-bromo-4-(aminomethyl)-5-fluorobenzofuran, which is then hydrogenated, at a reaction temperature of 40-100°C for a reaction time of 24-48 h, to obtain (5-fluoro-2,3-dihydrobenzofuran-4-yl)methylamine or a salt thereof.