With the transition towards the trend of multifunctional urban development, various types of public spaces have become increasingly integrated and polysemous. As a unique form of urban public space and an integral part of underground commercial streets, entrance spaces not only serve as vital nodes connecting above ground and underground areas but also as focal points accommodating diverse urban activities. However, many underground commercial street entrances in Northeast China face challenges such as aging facilities, outdated functions, and low spatial utilization rates, resulting in insufficient vitality and an inability to meet the diverse needs of modern urban life. Implementing scientific and reasonable strategies for renewal and revitalization to fully unlock the potential of these entrance spaces has become essential for improving the quality of underground commercial streets and enhancing the overall vibrancy of urban public spaces. A typological approach was adopted to categorize existing underground commercial street entrances in Northeast China. From the perspective of polysemy, it establishes an evaluation system based on three dimensions: environmental relationality, perceptual process, and functional ambiguity. By distributing questionnaires to experts and residents, it identifies and compares the influencing factors of entrance space polysemy and assigns values to polysemy indicators. Based on the evaluation results, the entrances are classified into categories of polysemy, and typical underground commercial street entrance spaces catering to diverse activity demands are summarized. Finally, optimization strategies for the polysemy of these typical entrance spaces are proposed to promote the renewal of existing underground commercial street entrances, meet the diverse needs of citizens, and enhance the vitality of urban underground spaces.