An asymmetry A0g = (g+ - g-)/(g+ - g-), where g+ and g- are the Dalitz plot slope parameters for K+ and K- decays into three pions, respectively, is a measure of a direct CP-violation in corresponding decays. This asymmetry has been measured using more than 40 millions of K± -> π± π0 π0 decays accumulated in 2003 run at CERN SPS with a precision, which is almost one order of magnitude better than in other experiments.