The invention discloses a method for detecting an MLL-AF4 fusion gene. The method sequentially comprises the following steps: 1, acquiring sample DNA, 2, preparing a PCR reaction liquid, wherein a primer used for amplifying the MLL-AF4 fusion gene is F: 5'-CCGCCCAAGTATCCCTGTAAAC-3', and a primer used for amplifying the MLL-AF4 fusion gene is R: 3'-TCGTTATGTATGCGGATCATGTCG-5', 3, carrying out target strip amplification by taking the DNA of a to-be-detected sample as a template, and amplifying a required DNA fragment through the designed primers, 4, carrying out target DNA recovery by carrying out 1% agarose gel electrophoresis on the PCR reaction solution, and recovering a target strip, 5, purifying the DNA fragments obtained in the step 1, 6, carrying out conversion on the purified DNA, and 7, carrying out sequencing, and judging whether the fusion gene is the MLL-AF4 fusion gene or not. According to the method for detecting the MLL-AF4 fusion gene, primers suitable for PCR amplification are designed, high specificity, accuracy and sensitivity are achieved in the detection process, a target band is amplified more rapidly and efficiently, and repeatability is achieved.