This paper presented a multi-band conformal MIMO antenna for unmanned aerial vehicles. The antenna is composed of four equally-sized mutually orthogonal meta-material radiating elements, a center-fed decoupling structure with a resonant aperture ring, and a back cross dumbbell-shaped structure. Simulated results show that the antenna operates in four frequency bands (2.07 GHz-2.84 GHz, 4.89 GHz-6.99 GHz, 8.19 GHz-9.10 GHz, 10.22 GHz-11.19 GHz), with a maximum gain of up to 3 dBi and a highest isolation of −54 dB. The overall size of the antenna is $71.1\times 71.1\ \mathrm{m}^{2}$, and the dielectric substrate is made of flexible polyimide material with a thickness of 0.13 mm, allowing the antenna to be conformal to the UAV body. This antenna can be widely used in UAV communications, 5G communications, and IoT.