Accurate and rapid aflatoxin B1 (AFB1) detection is essential for ensuring the safety of food supplies. In this paper, we introduce a distance-readout paper-based microfluidic chip (DPMC) that offers a sensitive and reliable method for the detection of AFB1. The DPMC comprises a DNA hydrogel sensitive valve and a paper-based capillary channel. Upon exposure to AFB1, the hydrogel valve regulates the flow speed of the tested liquid into the capillary channel. Quantitative detection of AFB1 can be achieved without the need for complex instrumentation for external equipment by visually observing the distance traveled by the tested liquid through the capillary channel over a specified period. Under optimal conditions, the DPMC allows for quantitative detection of AFB1 solution concentrations ranging from 100 to 1000 pM by the naked eye, with a detection limit of 17.64 pM. This method has been successfully employed for quantitative detection of AFB1 in lotus seed samples, yielding a recovery rate between 85.2% and 118.4%. This approach provides a rapid, portable, sensitive, and highly selective visualization platform for on-site AFB1 detection.