The invention discloses a method for detection of arsenic content in pyrite or pyrite concentrate by atomic fluorescence spectrophotometry. The method includes: (1) drying pyrite or pyrite concentrate to a constant weight, and conducting crushing and sieving; (2) taking 0.2g of a sieved sample and putting the sample into a 150mL container, adding 15mL of hydrochloric acid, and conducting heating and dissolving, then adding 5mL of nitric acid, and performing heating to a wet salt state; (3) adding 5mL of hydrochloric acid into a wet salt sample, performing cooling, then transferring the mixture into a 100mL volumetric flask, adding 10mL of a thiourea-ascorbic acid mixed solution or a thiourea solution, adding water for dilution to a constant volume, and performing dry filtration, discarding the initial 20mL of filtrate, shifting 1mL of filtrate into a 50mL volumetric flask, then adding water for dilution to a constant volume, thus obtaining a sample solution; and (4) using an atomic fluorescence spectrophotometer to measure the fluorescence intensity of the sample solution obtained in (3), and working out the content of arsenic in the pyrite or pyrite concentrate sample solution. The method provided by the invention can effectively improve the dissolution thoroughness of arsenic in pyrite and sulfur concentrate, improve the reduction degree of arsenic, reduce the loss rate of arsenic, and enhance the accuracy and precision of arsenic in pyrite and sulfur concentrate.