To expand the preparation scenarios of instant high-viscosity asphalt, a pure stirring process with varying stirring time is used to produce the instant high-viscosity asphalt. The key technical indicators of softening point, ductility, dynamic viscosity and apparent viscosity of the instant high-viscosity asphalt are analyzed, including the variation laws of the high-temperature stability, low-temperature crack resistance, water stability and anti-scattering characteristics of the corresponding SMA-8 mixture with the stirring time. The results show that as the stirring time increases from 2.5 h to 4.0 h, various performance indicators of the instant high-viscosity asphalt improves by approximately 10%. A pure stirring process of 2.5 h is sufficient to produce an instant high-viscosity asphalt mixture with performance comparable to that of the "shearing + stirring" process. The optimal stirring process is determined to be 2.5 h at 180 °C. The technical indicators of the laboratory samples and factory finished products under this process are close to those of the finished products from the traditional "shearing + stirring" process.