  The proton spin structure is not understood yet and there has remained large
uncertainty on Delta g, the gluon spin contribution to the proton. Double
helicity asymmetry (A_LL) of pi0 production in polarized pp collisions is used
to constrain Delta g. In this report, preliminary results of A_LL of pi0 in pp
collisions at sqrt(s) = 62.4 GeV measured by PHENIX experiment in 2006 is
presented. It can probe higer x region than the previously reported pi0 A_LL at
sqrt(s) = 200 GeV thanks to the lower center of mass energy.
