Abstract: The design of orthogogal waveform is one of key technology to realize MIMO radar. Presently, some statistical optimization arithmetic, such as SA (Simulated Annealing) and GA (Genetic Algorithms),is often used to design orthogonal waveforms for MIMO radar. The common flaws of before-mentioned method are low efficiency and the performance of waveform set should descend along with the increase of the waveform number. So a new method based on chaos frequency modulation signal is proposed to design orthogonal waveform set for MIMO radar. Because of the well statistic characteristic, the good orthogonal waveform set is gotten without using optimization arithmetic. Moreover, the waveform number would not affect the performance of waveform set. So the proposed method has advantage at arithmetic efficiency and waveform diversity. The simulations indicated the validity of the method.