The invention discloses a method for detecting N1-methyladenine by using a Ti-MOF based photoelectrochemical sensor, and a construction method of the sensor; the method comprises the following steps of sequentially modifying heterogeneous junctions of graphite-phase carbon nitride and bismuth vanadate, 4.0 generation polyamide-amine, p-carboxyl phenylboronic acid, m1A antibody, m1ATP, TiO2@NH2-MIL-125 (Ti) on the surface of a basic electrode to prepare the photoelectrochemical sensor. According to the method, by virtue of the photoelectric activity and biocompatibility of the heterogeneous junctions of the graphite-phase carbon nitride and the bismuth vanadate, and the specific recognition performance of the antibody to the antigen, and by taking the TiO2@NH2-MIL-125 (Ti) as a signal expansion unit, high sensitivity and high specificity detection on N1-methyladenine can be realized. Ti-MOF is used for identifying N1-methyladenine for the first time; and in addition, the detection method is simple, the miniaturization of the instrument is realized, the operation is easy, and the detection of the N1-methyladenine can be realized.