The test bed of digital multi input multi output (MIMO) radar in sub array level is developed and realized. Orthogonal binary phased shift keying signals are exploited in the subarray level. The transmit and receive digital beam forming is implemented in the receiving channel, and the observation of civil aircraft is accomplished successfully. The complexity of system design reduces greatly with the implementation of the orthogonal transmitting wave and multi beam techniques in subarray level, which is promising for engineering application. The MIMO radar function can be utilized as a kind of typical working mode in the digital array radar.