Abstract: To address the limited image reconstruction capability of the wavefield extrapolation method in heterogeneous layered media with nonuniform lateral sound speed, split step phase shift migration based photoacoustic imaging in heterogeneous medium is proposed. This method treats the lateral sound speed difference as an equivalent perturbation sound source at the interface of the layered medium. Such a virtual perturbation sound source can be used to generate additional corrective phase shifts on the reconstructive acoustic field. By employing a hybrid extrapolation mechanism with variable step size, layer-by-layer reconstruction of the photoacoustic wave field can be achieved. Both simulation and experimental results demonstrate that the proposed split step phase shift migration method can effectively suppress the generation of artifacts in photoacoustic imaging in irregular layered media, enhance image resolution, and improve image contrast.