Abstract: To improve microplastic detection efficiency, a lensless digital holographic method is proposed for analyzing microplastics in drinking water. A compact portable imaging device is developed using a light source, diaphragm, image sensor, and sample holder, significantly simplifying system design and testing procedures. Results show holographic reconstruction distances of microplastics concentrate at 2 300~2 900 μm, while non-microplastic particles cluster at 1 700~2 250 μm. The microplastic particles exhibit low intensity of interference patterns, weak contrast of interference fringes, and nearly circular interference rings with good symmetry. Solar radiation and high temperatures accelerate microplastic leaching. The device achieves 5 μm resolution with testing cycles under 5 minutes, offering advantages of small size, wide field-of-view, high resolution, rapid imaging, and ease of use. This work provides a novel technical solution for water quality monitoring.