Compared with traditional optical microscopes, lensless holographic imaging technology can provide large field-of-view cell images without the need for any lenses. Therefore, lensless holographic imaging can be widely used in biological detection and diagnosis. Based on the theory of physical optics, this article designs a lensless holographic imaging experimental device. Combining the designed experimental device with a method of determining the reconstruction distance by calculating the phase distribution, it can complete the construction of reconstruction images of animal and plant cells with diameters ranging from 5 to 40 μm, with an imaging range >20 mm2. This method can statistically analyze various characteristics of cells, with an accuracy rate of ∼92% for quantity and over 90% for diameter and area. It has great potential in medical detection.