The localized-itinerant nature of Ce-4 f valence electrons in heavy fermion compound CeIn 3 under pressure is studied thoroughly by means of the combination of density functional theory and single-site dynamical meanfield theory. The detailed evolutions of electronic structures of CeIn 3 , including total and partial density of states, momentum-resolved spectral functions, and valence state histograms etc., are calculated in a wide pressure range where the corresponding volume compression V/V 0 ∈ [0.6, 1.0] (here V 0 is the experimental crystal volume) at T 116 K. Upon increasing pressure, two strong peaks associated with the Ce-4 f states emerge near the Fermi level, and the c-f hybridization and valence state fluctuation are enhanced remarkably. Moreover, the kinetic and potential energies raise, while the occupancy, total angular momentum, and low-energy scattering rate of the Ce-4 f electrons decline with respect to pressure. All the physical observables considered here exhibit prominent kinks or fluctuations in V/V 0 ∈ [0.80, 0.90], which are probably the desired fingerprints for the Ce-4 f localized-itinerant crossover.