The experiment of the 50m(2) RPC carpet, carried out at Yang Ba Jing, Tibet
, is studied using Monte Carlo simulation. The simulation can re-produce th
e non-uniform azimuth angle distribution shown in experiment data and reach
es the conclusion that it is due to different reconstrucion errors in x and
y directions on asymmetic carpet (8.6 x 6.1 m(2)). Moreover, using the sim
ulation data, the angular resolution and energy spectrum ate given out.