There are many advantages for MIMO OFDM system, like spatial diversity, frequency diversity, ISI resistant…and so on. MIMO OFDM has become a key feature for Many communication standards(WiMAX LTE WiFi). From this paper, we want to investigate that while we rotate the phase of signal, whether or not the design will lead to batter BER. We try to find optimal phase shift for two receiver, MMSE equalizer and Matched filter. At last, we apply our designs in high speed environment.