Cancer has become one of the most common diseases with high mortality in humans. Early and accurate diagnosis of cancer is of great significance to enhance the survival rate of patients. Therefore, effective molecular ligands capable of selectively recognizing cancer are urgently needed. In this work, we identified a new DNA aptamer named SW1 by tissue-based systematic evolution of ligands by exponential enrichment (tissue-SELEX), in which cancerous liver tissue sections were used as the positive control and adjacent normal liver tissue sections were used as the negative control. Taking immobilized liver cancer SMMC-7721 cells as the research object, aptamer SW1 exhibited excellent affinity with a Kd value of 123.62 ± 17.53 nM, and its binding target was preliminarily determined as a non-nucleic acid substance in the nucleus. Moreover, tissue imaging results showed that SW1 explicitly recognized cancerous liver tissues with a high detection rate of 72.7% but displayed a low detection rate to adjacent normal tissues. In addition to liver cancer cells and tissues, aptamer SW1 has been demonstrated to recognize various other types of cancer cells and tissues. Furthermore, SW1-A, an optimized aptamer of SW1, maintained its excellent affinity toward liver cancer cells and tissues. Collectively, these results indicate that SW1 possesses great potential for use as an effective molecular probe for clinical diagnosis of cancer.