  We proposed a new universal method for significantly increasing accuracy of
critical points of 2 and 3-dimensional Ising models and exploring fluctuation
mechanism. The method is based on analysis of block fractals and the
renormalization group theory. We discussed hierarchies and rescaling rule of
the self similar transformations, and define a fractal dimension of an ordered
block, which minimum corresponds to a fixed point of the transformations. By
the connectivity we divide the blocks into two types: irreducible and
reducible. We find there are two block spin states: single state and k-fold
state, each of which relates to a system or a subsystem described by a block
spin Gaussian model set up by mathematic map. Using the model we obtain a
universal formula of critical points by the minimal fractal dimensions. We
computed the critical points with high accuracy for three Ising models. It is
the first time to find a critical point only requires a fractal edge, which
causes fluctuations, and the point acts as a fluctuation attractor. Finally, we
discussed a possibility of different block spins at the critical point.
