K-band, as an important application frequency band in the microwave frequency band, is widely used in wireless communication, RF identification and civil radar. And K-band microstrip antenna has become a research hotspot in recent years due to its advantages of small size and good directionality. In this paper, a miniaturized Multiple-input Multiple-output (MIMO) antenna is designed to widen the bandwidth of the antenna by cutting the angle of the radiating patch and digging a slot in the ground plane; meanwhile, a raised rectangular parasitic branch with an open slot is placed on the ground plane and a Complementary Split-Ring Resonator (CSRR) is etched to generate a resonance at a fixed frequency point. resonance at a fixed frequency point, effectively reducing the mutual coupling. The simulated and measured results show that the overall size of the antenna is only 15×24×0.8mm3, the overall isolation is less than -18.3dB in the operating bandwidth range of 17~27.2GHz（relative bandwidth reaches 46.2%）, and the Envelope Correlation Coefficient (ECC) is less than 0.001, so the designed K-band MIMO antenna has good radiation characteristics and gain