The invention discloses an iterative least square method-based 
MIMO (
multiple input multiple output) 
radar DOA (direction-of-arrival) 
estimation method, which is characterized in that receiving and transmitting array response matrixes on which dimension-reduced 
processing is performed are solved by using an iterative least square method. The iterative least square method-based 
MIMO radar DOA 
estimation method comprises the following steps: firstly, performing the dimension-reduced 
processing on echo data matrixes of multiple 
radar transmitted pulses and the receiving and transmitting array response matrixes; then, establishing cost functions under the least square condition, and solving the cost functions by utilizing a 
gradient descent-based 
iterative method; finally, estimating the direction of a target by utilizing known receiving and transmitting array manifolds. Compared with a traditional monostatic 
MIMO radar array DOA 
estimation method, the iterative least square method-based 
MIMO radar DOA estimation method disclosed by the invention directly obtains the DOA estimation of the target, and does not need to perform spectrum peak search. 
Noise is effectively suppressed by adopting the dimension-reduced 
processing, and the estimation accuracy under low 
signal to 
noise ratio is improved; the estimation, the inversion and the eigenvalue 
decomposition operation of high-dimensional data 
covariance matrixes are avoided; the defects that the calculated amount is high and the needed 
sample number is large when the traditional array DOA estimation method is applied to a monostatic 
MIMO radar are overcome.