Muon scattering tomography (MST) is a promising technique for detecting high-Z materials. However, developing such detectors with both high spatial resolution and a large detection area, especially on a limited budget, is challenging. This study aims to develop a position-sensitive muon detector with a large detection area and high spatial resolution. We chose a plastic scintillation detector as our solution because it is cost-effective and easy to fabricate. The effective area of the detector is larger than 50 cm×50 cm with a 1.1 cm pitch and can be easily expanded to larger sizes. A readout system with encoded signals, which reduces the number of readout channels by one-fourth, has been developed. The detector also exhibits excellent performance in spatial resolution and detection efficiency, measured to be 1.5 mm under cosmic rays, indicating great potential for muon scattering tomography.