The melting effect of different direct-injection modifiers and aggregates under different conditions is studied by three-dimensional microscopic observation method; base asphalt and 4.5SBS modified asphalt and four direct-injection modifiers are used for dry mixing. To explore the possibility of further improving the performance of the direct-input modified asphalt mixture, and to study the various properties of the asphalt mixture through the Kentenburg flying test, the Hamburg rutting test, and the freeze-thaw splitting test. Studies have shown that: different direct-injection modifiers should be selected according to their melting effect with aggregates and the corresponding dry-mixing temperature and dry-mixing time; the anti-scattering performance of the mixture made of base asphalt and direct-injection modifiers, The high temperature performance and water stability performance are significantly improved compared to the base asphalt mixture, but the water stability performance still does not meet the specifications; 4.5 SBS modified asphalt is dry mixed with four direct-input modifiers, and the performance of the mixture is uniform. Further improvement, among them, the water stability performance of each mixture meets the specification requirements; the modification effect of GPJ direct injection modifier is the most significant.