Enterovirus alphacoxsackie (EV-A) is a highly diverse viral species containing at least 25 serotypes of viruses which show distinct infectivity and pathogenicity. Increasing studies show that EV-A protease 2A plays critical roles in virus-host interactions. Although 2A is usually considered as a non-structural protein highly conserved among different EV-A serotypes, its orthologs of different EV-A serotypes harbor abundant single amino acid polymorphisms (SAPs), probably contributing to the variance of infectivity and patho-genicity of EV-As. However, the SAP profile of EV-A 2A and its functional impacts have been poorly understood, mainly due to the unequal contribution to protein function of dif-ferent SAP sites. Herein, we developed Single Amino Acid Polymorphism Statistics (SAAPS), an information-entropy-based algorithmic pipeline, to identify key SAP sites (kSAPs) related to functional variance of EV-A 2A. As the result, we identified 56 kSAPs from 2A of 25 EV-A serotypes. Based on the kSAPs, the 2As can be clustered into three major groups with a few outliers, which was distinct from the clustering generated by phylogenetic analysis using the whole amino acid sequences. Functional verification with transcriptomic profiles of HEK-293T cells expressing different 2A variants revealed better phenotypic matching of kSAP-based clustering than that of phylogenetic clustering. No-tably, EV-A89, an outlier identified by kSAP clustering but not phylogenetic clustering, showed unique expressing and self-cleavage patterns which were not observed in other 2As. These findings demonstrated the good performance of SAAPS and functional SAP profile of EVA 2As, contributing to the understanding of the variance of EV-A infectivity and pathogenicity.