Abstract: The transmit array of phased MIMO radar is partitioned into a number of sub-arrays which are fully-overlapped. The phased MIMO radar beam pattern is expressed as the product of transmit beam pattern, waveform diversity beam pattern and receive beam pattern. The beam forming of phased MIMO radar is mainly studied, through analyzing the maximum radar range, highest sidelobe, width of mainlobe and achievable output signal-to-interference-plus-noise ratios. Compared with phased array radar and MIMO radar of the same configuration, theory and simulation results show that phased MIMO radar has better performance on sidelobe suppression and anti-interference. Finally, the optimal sub-array number under different conditions is obtained.