Nanozyme-based colorimetry used in the 3,3 ',5,5 '-tetramethylbenzidine (TMB) chromogenic system for detecting ascorbic acid related bio-enzymes has shown great potential. However, TMB faces limitations due to its high cost, hydrophobicity, and tendency to solidify at low temperatures. In this study, a bimetallic Mn/Fe covalent organic polymers nanozyme (Mn/Fe COP) was designed with high laccase-like activity, which was able to catalyze the oxidation of 4-AP to red oxide product with the assistance of 2,4-dichlorophenol (2,4-DP). Surprisingly, the ascorbic acid was significantly reduced the oxidation, resulting in a noticeable fading of the red color. Therefore, a novel colorimetric platform for sensing the ascorbic acid was developed by the 2,4-DP/4-AP reaction system catalyzed by Mn/Fe COP. Obviously, this colorimetric platform was capable of quantifying ascorbic acid-related biological enzymes. Here, we report a proof-of-concept study on the determination of alpha-glucosidase (alpha-Glu) using the proposed sensing system, which catalyzed the the decomposition of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid into ascorbic acid with the aid of alpha-Glu. Finally, a simple and sensitive colorimetric method was developed for detecting alpha-Glu activity, achieving a detection limit of 4.6 mU & sdot;mL- 1 and a linear range from 0.01 to 1.2 U & sdot;mL- 1. Furthermore, the designed sensing platform exhibits favorable applicability for the alpha-Glu assay in human serum samples and expanded to study the inhibitors of alpha-Glu.