  We investigate the evolution of the global string network in the radiation
dominated universe by use of numerical simulations in 3+1 dimensions. We find
that the global string network settles down to the scaling regime where the
energy density of global strings, $\rho_{s}$, is given by $\rho_{s} = \xi \mu /
t^2$ with $\mu$ the string tension per unit length and the scaling parameter,
$\xi \sim (0.9-1.3)$, irrespective of the cosmic time. We also find that the
loop distribution function can be fitted with that predicted by the so-called
one scale model. Concretely, the number density, $n_{l}(t)$, of the loop with
the length, $l$, is given by $n_{l}(t) = \nu/[t^{3/2} (l + \kappa t)^{5/2}]$
where $\nu \sim 0.0865$ and $\kappa$ is related with the Nambu-Goldstone(NG)
boson radiation power from global strings, $P$, as $P = \kappa \mu$ with
$\kappa \sim 0.535$. Therefore, the loop production function also scales and
the typical scale of produced loops is nearly the horizon distance. Thus, the
evolution of the global string network in the radiation dominated universe can
be well described by the one scale model in contrast with that of the local
string network.
