The invention relates to a preparation method of an in-situ toughening hard rubber material of vulcanized rubber powder. In the preparation method, sulfur in the hard rubber material is prevented from moving inwards in presence of the cross-linked network inside the vulcanized rubber powder, and diffusion gradient is formed at the interface to form a modulus transition interface from hard to soft so as to have the effect of toughening the hard rubber. The prepared hard rubber material has a tensile strength of 60MPa, a tensile modulus of 2GPa, a hardness more than D80 degrees and a non-notch impact strength over 120KJ/m3. The preparation method is simple and easy to execute, has wide source of raw materials and low cost, and the prepared material can be recycled, thereby having important social, economic and environmental benefits.