In this paper, a low computational complexity Orthogonal frequency-division multiplexing Multiple Input -MultipleOutput (OFDM -MIMO) decoder for the 802.11ac Wireless Local Area Network (WLAN) is addressed. To reduce the computational complexity of the conventional K-Best algorithm, the combination of two new approaches to determine the K-best nodes are introduced. The first approach is the constellation I-Q plane based sorting method to sort one-dimension vector in ascending order. The second one is the table based sorting method to sort a two dimension -vector in ascending order. By simulation results, the Bit Error Rate (BER) performance of our proposed approaches is only degraded 0.5 dB compared with that of the conventional K-Best algorithm, but our proposal helps to reduce up to 90% of the computational complexity in term of sorting method.