A genetic algorithm-based deployment optimization model was proposed for anti-low-slow-small unmanned aerial vehicle （anti-LSS-UAV） systems in key low-altitude areas. It focused on key low-altitude areas and integrated UAV trajectory and force requirement models. An objective function was constructed by comprehensively considering factors such as environmental score， enemy attack probability distribution， and target detection/engagement success probability. Through comparative analysis with the compressed factor particle swarm optimization-genetic hybrid algorithm and the compressed factor particle swarm optimization algorithm， the genetic algorithm achieved a higher probability of reaching the global optimal deployment scheme within 50 iterations under the same environment， a lower average deviation， and thus higher reliability. To improve the reliability， the 100-iteration genetic algorithm was adopted as the algorithm for the deployment optimization model.

With the rapid development of information equipment， the combat style is also changing and improving， and the cross domain distributed operation through air ground coordination will become inevitable. The air combat platform has the advantages of good mobility， broad vision and strong situational awareness， while the ground defense equipment has the advantages of concealed deployment， wide firepower coverage and strong anti-interference ability. Adopting the distributed coordination mode of air and ground can give full play to their respective advantages， improve the utilization rate of equipment of all services and arms， and achieve greater operational efficiency. In the future， air ground cooperative operations will be characterized by “three-dimensional unity， air to ground coordination， and multiple divisions in one region”。The necessity of cross domain distributed operation through air ground coordination is put forward in this paper for future battlefield characteristics. The characteristics of cross domain distributed defense are given. The shortcomings of the current defense operation architecture are analyzed， and the specific measures of air ground cooperative cross domain distributed defense are analyzed. The key technologies of cross domain distributed defense are summarized and the development suggestions are given.

With the rapid development of unmanned aerial vehicle（UAV）， UAVs have been widely used in civil and military fields. Small UAVs with “low flight height， slow flight speed and small dimensions” characteristics are especially convenient and flexible to use and relatively inexpensive. They can be used for reconnaissance， surveillance，suicide attack and other task purposes， posing a serious threat to daily air defense security and important assets protection. The main threat patterns of the small reconnaissance UAV and payload capabilities are analized. The denial distance requirements to small UAVs are also proposed， which can provide reference for anti-UAV system development .