Abstract: Objectives To address the urgent demand for high-reliability and high-rate data transmission in shipboard communication systems, a dual-element MIMO antenna design operating simultaneously at 915 MHz and 5.8 GHz ISM bands is proposed.Methods The antenna is fed by microstrip lines, with two closed resonant loops serving as radiating elements to cover the 915 MHz and 5.8 GHz bands respectively. A neutralization line and a rectangular parasitic stub are loaded between the two antenna elements to form a composite decoupling structure, thereby enhancing inter-element isolation. A U-shaped notch is etched on the feeding microstrip line to suppress the unwanted resonance at 2.85 GHz. The antenna is fabricated on an FR-4 dielectric substrate with an overall size of 103 mm×96 mm×1 mm.Results Both simulation and measurement results demonstrate that <italic>S</italic>₁₁&lt;−10 dB within both target frequency bands, with in-band isolation greater than 15 dB, envelope correlation coefficient (ECC) below 0.02, and diversity gain (DG) exceeding 9.99.Conclusions The proposed dual-loop radiating structure, composite decoupling scheme, and notch technique enable dual ISM-band coverage, out-of-band resonance suppression, and compliance with the channel independence requirements of MIMO systems under a compact inter-element spacing of 0.14 wavelengths at 915 MHz, providing a viable engineering reference for shipboard dual-band MIMO antenna design.