The present invention discloses a method for detecting an invasive alien fish species comprising: extracting a DNA from a fish sample; subjecting the DNA to Loop-mediated Isothermal Amplification by using a primer set of the invasive alien fish species; detecting the invasive alien fish species by visualizing the amplified DNA under UV transillumination; wherein each of the primer sets comprises two outer primer, two inner primer and at least one loop primer; characterized by: the alien fish species comprising Poecilia reticulata, Carassius auratus, Betta splendens, Pterygoplichthys pardalis, Cyprinus carpio and Clarias gariepinus; the primer set of Poecilia reticulata comprises SEQ ID NO: 1 to 5; the primer set of Carassius auratus comprises SEQ ID NO: 6 to 11; the primer set of Betta splendens comprises SEQ ID NO: 12 to 17; the primer set of Pterygoplichthys pardalis comprises SEQ ID NO: 18 to 22; the primer set of Cyprinus carpio comprises SEQ ID NO: 23 to 27; and the primer set of Clarias gariepinus comprises SEQ ID NO: 28 to 32.