With the assessment method for current of interconnected lines has been changed from area control error（ACE） mode to control performance standard（CPS） mode in Central China Power Grid， the coordinate control between hydro units and thermal units for automatic generation control in Henan Power Grid becomes very important because of having a few hydro units. For this new condition， two control modes are proposed in this paper. Based on the experimental investigation on the coordinate control between hydro units and thermal units， the characteristics and effects of two control modes and different control schemes based on them are analyzed. Then the proper coordinate control scheme of hydro units and thermal units is presented. The further work are put forward to solve the problems found in the coordinate control experiment.