In order to apply the model predictive control to the power converter, a study on the calculation amount reduction algorithm was performed in various topologies such as 2-level, 3-level, multi-level converter. Similarly, in order to apply the model predictive control to the 3-level 4-leg converter, it is necessary to study the calculation amount reduction algorithm. In this paper, instead of considering 81 candidate voltage vectors for every sampling period as in the conventional model predictive control, the optimal switching state is selected considering only 7 candidate voltage vectors located near the reference voltage vector. The sector, prism, and tetrahedron are selected sequentially by using the position of the reference voltage vector, and the preselected 7 candidate voltage vectors are the vectors constituting the tetrahedron. The proposed method represents an improved model predictive control which reduces the amount of computation and does not affect performance. This method constructs the 3-level 4-leg NPC inverter simulation and experimental setup to compare the performance with the conventional method.