Abstract: One trend in current whole-body PET scanner development is to increase the axial field-of-view. But the degradation of the spatial resolution of PET scanners due to depth of interaction uncertainty increases as the axial field-of-view increases. PET detector with depth encoding capability has become essential. In this work, a depth encoding PET detector using the side readout of duallayer semi-continuous crystals with the SiPM array was proposed. The upper layer of the detector is a fast 1×4 LYSO array, and the lower layer is a 1×4 YSO array. The size of each crystal in each layer is 3 mm×6 mm×18 mm. The crystals of each layer were separated by an ESR reflection film, and the crystal array of the upper and lower layers were coupled by optical glue. The experimental results show that the detector can effectively identify the two layer and all crystals can be clearly resolved from the flood histograms. For the upper and lower crystal array, the average energy resolution is 11.9% and 11.7%, respectively. The detector has a good position resolution of 0.27 mm (FWHM) for the crystals. The crystal resolution map can clearly distinguish all crystal units and provide continuous depth information in the z direction. The signal maximum and sum ratio method was used to analyze the y direction height position, and the upper LYSO crystal layer is better than the lower YSO crystal layer. The experimental results reveal that the novel PET detector proposed here can be used to achieve high-performance whole-body and panoramic PET scanners.