The invention discloses a hydraulic fracture complexity prediction method based on the residual stress levels of rock cores. The method is characterized by comprising the following steps: performing physical simulation tests on static rock mechanical parameters of sampled rock cores of an implemented well; performing numerical simulation tests on rock mechanical parameters based on numerical valuerock cores to obtain fine residual strength characteristics of reservoir rock masses; establishing different finite element analytical models for different reservoirs with different residual stress,and calculating hydraulic fracture complexity indexes for predicting hydraulic fracture complexity. The method can be used for catching the whole process of crack production and extension of complex fracture networks in real time, can realize advanced assessment of fracture complexity and guide fracturing construction design and has great significance in improving fracturing design and increasingcomplex fracture network volumes.