Objective: To develop an automated staining device addressing the issues of cumber some operation, low efficiency, and cluttered workspace associated with current clinical rapid on-site evaluation using Diff-Quik staining for aspiration specimen cytological smears. Methods: The device integrates a microcontroller to control motors, peristaltic pumps, solenoid valves, and fans, enabling the automatic transfer of cytological slides, delivery of staining and rinsing solutions, and forced-air drying. Results: Preliminary test results indicated that the developed device successfully performs four key steps, including Diff-Quik A and B staining, rinsing, and drying, achieving automatic staining of cytological smears. Conclusion: The developed device features a compact footprint and has no pollution to the operating environment, offering a practical solution for automated, efficient, and convenient slide staining during rapid on-site evaluation procedures.