  In this paper, two classes of exact analytic time-dependent soultion of
magnetic annihilation for incompressible magnetic fluid, have been obtained by
solving the magnetohydrodynamic (MHD) equations directly. The solutions derived
here possess scaling property with time $t$ as the scale factor. Based on these
two solutions, we find that, for some given inflow fields, the evolution of the
annihilating magnetic field can be described by the solutions of certain
ordinary differential equations whose variables are dilated simply by time $t$.
The relevant evolution characteristics in the process of magnetic annihilation
are also revealed.
