This paper presents a multiband compact microstrip MIMO antenna for Unmanned Air Vehicle, GPS and WLAN applications. It consists of two symmetric triangular spiral shape patch and defected ground structure (DGS). The antenna is designed using low cost FR4 Substrate and analysed by using commercially available electromagnetic simulation software CST. The simulation results shows the designed antenna has resonance frequencies at 1.62 GHz and bandwidth from1.6027 GHz to 1.6391 GHz, at 2.42 GHz from 2.3609 GHz to 2.4667 GHz and 3.79 GHz from 3.6418 GHz to 3.7909 GHz frequency which covers GPS, WLAN and UAV(LTE band) applications respectively. Detailed physical analysis of proposed antenna is presented and the characteristics of antenna are verified by the return loss, insertion loss, gain and directivity. It is found that it has good performance for above applications. The overall size of the antenna is 28 x 20.5 mm2 which is less than the conventional antenna by 84% at lowest resonating frequency of 1.62 GHz.