The invention discloses a manganese-dioxide-nanosheet-based oxalic acid detection kit and application thereof. The kit comprises a 96-pore polystyrene micro-pore plate, a manganese dioxide nanosheet solution, a sample diluent, a TMB color development solution and an HCI termination solution. 3 microlitres of manganese dioxide nanoplate solutions are added into the 96-pore polystyrene micro-pore plate; 100 microlitres of sample dilution solutions are added and reaction is made for 10 minutes; 100 microlitres of TMB color development solutions are added into the reacted solution and then the 100microlitres of HCI termination solutions are added to terminate the reaction; and the reacted 96-pore polystyrene micro-pore plate is placed into a microplate reader and fixed-point scanning of absorbance of the wavelength of 460 nm is performed. According to the invention, the specificity detection of the oxalic acid is performed by using the manganese dioxide nanosheet and the oxalic acid is detected quantitatively by adding the color development solution. The disclosed kit has advantages of low detection lower limit and short detection time.