  In this paper, the basic quantum field equations of free particle with
0-spin, 1-spin (for case of massless and mass $>$ 0) and 1/2 spin are derived
from Einstein equations under modified Kaluza-Klein metric, it shows that the
equations of quantum fields can be interpreted as pure geometry properties of
curved higher-dimensional time-space . One will find that if we interpret the
5th and 6th dimension as ``extra'' time dimension, the particle's wave-function
can be naturally interpreted as a single particle moving along geodesic path in
6-dimensional modified Kaluza-Klein time-space. As the result, the fundamental
physical effect of quantum theory such as double-slit interference of single
particle, statistical effect of wave-function, wave-packet collapse, spin,
Bose-Einstein condensation, Pauli exclusive principle can be interpreted as
``classical'' behavior in new time-space. In the last part of this paper, we
will coupling field equations of 0-spin, 1-spin and 1/2-spin particles with
gravity equations.
