The brittleness of glutenite core is closely related to the hydraulic fracturing in oil and gas fields. It is of great significance to analyze the influence of the brittleness characteristics of glutenite reservoir on the complexity of hydraulic fractures to provide reference for the selection of target layers and the design of hydraculic fracturing process. Considering the brittleness characteristics of the whole process of rock failure（i.e.，the pre-peak and post-peak stages），a reservoir rock brittleness evaluation model based on the energy dissipation of the whole process of core failure is proposed. The accuracy of the model is verified by using the uniaxial and triaxial total stress-strain curves of glutenite and the existing brittleness evaluation model. The correlation between the core mechanical parameters and brittleness index under the different confining pressures is analyzed，and the effects of the brittleness index on hydraulic fracture complexity is studied by using the results of the laboratory test and microseismic monitoring of hydraulic fractures. The results show that the brittleness evaluation model can comprehensively evaluate the brittleness characteristics of the whole process of core failure，which is more sensitive to the brittleness changes of rocks with different lithology and different confining pressure than the traditional brittleness evaluation models. The parameters of core strength and elastic modulus under the different confining pressures have negative correlation with the brittleness index. The layers with the strong brittleness are more likely to form complex fractures through hydraulic fracturing，and obtain bigger stimulated reservoir volume（SRV）. It is feasible to predict and analyze the complexity of hydraulic fracture according to the brittleness characteristics of core.