  We present the preliminary results from our analysis of event by event
fluctuation in K/pi ratio in Au+Au collision at \sqrt s_{NN} = 200 GeV and at
62.4 GeV using STAR detector at RHIC. Two different methods have been used to
extract the strength of dynamical fluctuation and the centrality dependence of
that. The results from the study of energy and centrality dependence of the
dynamical fluctuation are presented. From the excitation function it is seen
that at two RHIC energies the measure of dynamical fluctuation is constant with
values very close to that at 12.3 GeV at SPS. The dynamical fluctuation is
found to be positive and decreasing with increasing centrality at RHIC. The
results are compared with HIJING model calculation with jets. Results from
HIJING are found to be very close to data from central collisions whereas it
over predicts the data for peripheral events.
