Since its invention, the scanning tunneling microscope (STM) has played a pivotal role in surface science and nanotechnology due to its exceptional atomic-resolution imaging capability. In recent years, although high-end STMs have enabled breakthroughs under extreme conditions, their high cost and operational complexity hinder widespread adoption in education and routine inspection. This paper presents a compact, cost-effective, and high-performance portable STM system developed entirely in-house. The system comprises a piezoelectric scanner, coarse approach stepper motor, low-noise signal detection circuit, STM32H7-based control unit, and a Qt-based user interface, all built from the ground up. A modular microscope body integrates a passive vibration isolation system, and the mechanical decoupling of the scanner and motor enhances imaging stability. Experimental results demonstrate high signal precision, with controller voltage resolution better than 0.6 mV. The stepper motor operates reliably, with a no-load starting voltage of 17 V (down) to 24 V (up) and step sizes ranging from 0.33 μm (17 V) to 2.01 μm (80 V). The custom-developed scanner initiates movement at 20 V (down) to 29 V (up), with step sizes from 0.21 μm (17 V) to 1.26 μm (80 V). The scanner structure is compact and rigid, with measured thermal drift rates of 31.5 pm/min (X-Y) and 42.3 pm/min (Z) on a ground-floor lab, and 44.8 pm/min (X-Y) and 56.2 pm/min (Z) on a third-floor desktop, reflecting excellent structural and electronic stability. Ultimately, the system achieves atomic-resolution imaging under ambient conditions, with high imaging consistency and control precision, making it suitable for scientific research, teaching, and industrial surface characterization.