The angle estimation algorithms of multiple input and multiple out (MIMO) radar are studied. Based on cross array in monostatic MIMO radar, a new algorithm for parameter estimation is proposed by employing quaternion theory to angle e stimation of MIMO radar. Through the construction of quaternion model, the enha ncement matrix, whose rank is equal to the number of targets and has no relatio ns with the coherency of the targets, can be got combining with matrix enh ancement and matrix pencil (MEMP) algorithm. Then the two dimensional angle of coherent targets can be estimated combining with ESPRIT algorithm. This algor ithm, avoiding peak searching which consumes much time and realizing angle esti mation of coherent targets with automatic pairing, has a lower computation compl exity and is more applicable in practice. Simulation results verify that th e proposed algorithm is effective.