In conclusion, we have developed new aptamer probes for specific recognition of the AGR2. In the SELEX process, AGR2-GST fused protein was used as the target protein, and linked to sepharose beads through the mild, yet specific, noncovalent GST-Glutathione interaction. Beads-based SELEX allowed the use of simple, yet effective, flow cytometry analysis to monitor the progress of the selection, avoiding the tedious, time consuming and radioactive EMSA process. Through multiple rounds of selection with GST as a control, we have identified aptamers that selectively recognize AGR2 with nanomolar K d values. CD measurements and melting-temperature assays demonstrated that the optimal aptamer C14B1 forms an intramolecular parallel G-quadruplex structure and its structure and binding affinity are strongly dependent on the nature of the monovalent ion. Furthermore, with our design of AGR2-aMB, AGR2 could be sensitively and selectively detected The aptamer sequences and sensors reported here has great potential to serve as a useful tool for early diagnosis and prognosis of cancer and for fundamental research to elucidate the biochemical functions of AGR2.