A huge demand and supply gap existed in the market about leather identification. The nondestructive detection method of different kinds of leather, especially different kinds of natural leather, has important application value. The terahertz (THz) transmission spectra of different kinds of natural leather and artificial leather have been systematically investigated and compared by THz time-domain spectroscopy (THz-TDS). In the range of 0.2 to 1.5 THz, the THz absorption coefficient and refractive index of natural leather are generally greater than those of artificial leather, and those of reptile leather, fish leather and mammal leather gradually decreased. There existed a turning point at about 60 ℃ in the amplitude change of THz time-domain spectroscopic curve during the heating process of natural leather from 25 to 80 ℃ with different variation tendency to pigskin, cowhide and sheepskin respectively, while it is absent to artificial leather. Further, the THz spectrum feathers of major components of leather, collagen, Polyvinyl chloride (PVC) and Polyurethane (PU) have been characterized to verify the cause of the difference of leather THz spectrum. The THz absorption coefficient and refractive index of collagen are greater than those of PVC and PU. The inflection point appears to collagen, but not to PVC during the same heating process. The characteristics of the THz spectrum of the composition of leather, collagen, PVC and PU have the similar numerical trends and changes, which indicates that the difference of the THz spectrum between different kinds of leather is mainly due to the difference in its composition. The work illustrates that the THz-TDS could be used to label-free distinguish artificial leather from natural leather and differentiate varieties of natural leathers from reptiles, mammals and fish.