Aiming at the Neutral-point-clamped(NPC) type three-level grid-connected inverters system, using sliding mode observer technology, a deadbeat optimizable finite control set model predictive control strategy is proposed based on sliding mode observer. Firstly,in order to reduce the grid current harmonic content and independent control of active and reactive power, a sliding mode observer is constructed based on the power function to realize real-time observation of grid voltage and coupling items. Then performance cost objective function is constructed based on the midpoint unbalanced voltage compensation to improve the performance of the control system. The simulation results show that the control strategy is reliable and effective. Secondly,Current deadbeat finite control set model predictive control(FCS-MPC) is proposed based on sliding mode observer and voltage space vector information to reduce control calculation.