Abstract: The usage of multi-input multi-output (MIMO) systems such as MIMO radar allows the array elements to transmit different waveforms freely. Waveform diversity offers more freedom and potential to improve the resolution, number of targets that could be identified, and flexibility in beam-pattern design. Recently, attention has been focused on MIMO radar high resolution imaging. To synthesize wideband signal, a new transmitting signal model was proposed with the combination of space-time 2-D stepped-frequency and linear frequency modulation. The wideband signal processing could be divided into four stages: receiving beam-forming, pulse compression, transmitting beam-forming and slow-time signal synthesis. Simulation shows that wideband MIMO radar, with a large number of array elements, can synthesize wideband signal within a PRT (pulse repetition time), and therefore avoid the conventional compensation for target motion.