Abstract: In this paper, the recent progress of free-standing diamond films prepared by DC (direct current) arc plasma jet is reviewed from arc characteristics, diamond crystal quality, mechanical properties, optical properties and thermal properties. The results shows that the crystalline quality and stress state of diamond films are different in various regions of arc, and that Ti transition layer can reduce the residual stress of diamond. The fracture toughness of diamond is up to 10.99 MPa·m^1/2 by four-point bending method. In a certain temperature range, the change tendency of the absorption coefficient and temperature is independent of the crystalline quality and thickness of diamond films. The better optical properties of diamond films are, the higher thermal conductivity is. The thermal conductivity of nucleation surface is slightly higher than that of growth surface. When temperature is more than 500 K, the thermal conductivity of polycrystalline diamond films could approach that of single crystal.