Excessive intake of aluminum ions poses a risk to human health; therefore, developing highly sensitive and rapid analytical methods for aluminum ion detection is of great significance. Among various techniques, electrochemical sensors have attracted attention due to their simple operation and fast response. In this study, an electrochemical sensor based on a polyornithine-modified glassy carbon electrode (POrn/GCE) using morin as a probe was constructed for the sensitive detection of aluminum ions, and its feasibility for practical sample analysis was evaluated. The polyornithine electrochemical sensor was prepared using cyclic voltammetry (CV). The surface morphology and electrochemical performance of the POrn/GCE were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Compared with the bare glassy carbon electrode (GCE), the POrn/GCE exhibited excellent electrocatalytic activity toward morin, with a significantly increased peak current. Since morin can form coordination complexes with aluminum ions, the oxidation peak current of morin at the POrn/GCE decreased with increasing aluminum ion concentration in the same solution. Based on this principle, an electrochemical sensor using morin as a probe was developed for aluminum ion detection. The linear range of the sensor was 8.0 × 10?? to 1.0 × 10?? mol·L?1, with a correlation coefficient R = 0.9983 and a detection limit of 6.00 × 10?? mol·L?1. The proposed electrode was successfully applied to determine aluminum ions in real samples, with recovery rates ranging from 97.87% to 106.38%. This method is simple, rapid, and accurate, and holds good application prospects in fields such as food safety.