The unsteady DDES method was used to study the time averaged flow characteristics and transient flow characteristics of slat system, and the far-field aerodynamic noise characteristics of slat system were evaluated and analyzed by FW-H method. The results show that: 1) In the with track no cavity configuration, there is a strong pulsation region of the flow field above the root of the track. In the with track with cavity configuration, there is a larger strong pulsation region of the flow field in the cavity and on the upper wing surface of the main wing; 2) A chordwise vortex pair structure similar to the flow around a square column appears around the track, which expands along the wing chord, and then is limited and squeezed by the wall of the cavity, and finally breaks into a large number of small vortices and dissipates; 3) In the spanwise symmetric plane, the no track no cavity configuration is similar to a typical dipole noise source; the with track no cavity configuration is also similar to a dipole source, while the principal axis rotates clockwise a little; the with track with cavity configuration shows asymmetry; 4) At 270° azimuth, the overall sound pressure level increment brought by the track and its cavity is about 7 dB and 2 dB respectively.