In this paper, a two-element tri-band CPW-fed millimeter-wave multiple input multiple output(MIMO) antenna is proposed for Internet of Things (IOT) applications. The antenna elements are parallel placed. The isolation is enhanced by utilizing the defected ground structure(DGS) and CSRR structure. The MIMO antenna is printed on substrate liquid crystal polymer(LCP) with a compact size of $\mathbf{11}\times \mathbf{22}\times \mathbf{0.1}\text{mm}^3$. The proposed antenna covers the frequency ranges of 16.94-19.31GHz, 27.64-30.45GHz and 37.39-40.09GHz. Furthermore, the MIMO antenna possesses an excellent isolation performance with the isolation of better than 21dB in the whole operating band. Moreover, the presented antenna realized low ECC of less than 0.05 with a high DG of 9.99dB. The presented MIMO antenna shows promising application prospect in KU band and 5G 28/38GH field.