In this paper, we design constant modulus probing waveforms with low correlation sidelobes for colocated multi-input multi-output (MIMO) radar. Through exploiting the structure of the problem, we formulate it as a non-convex consensus minimization problem. Then a customized alternating direction method of multipliers (ADMM) algorithm is proposed to solve the problem, which is guaranteed convergent to its stationary point. Numerical examples show that the proposed approach offers better performance than the state-of-the-art approaches. Moreover, parallel implementation structure indicates that the proposed ADMM algorithm is suitable for applications involving large dimensionality.