With the accelerated application of unmanned swarms to multidimensional domains such as space, air, ground, sea, and underwater, intelligent collaborative technologies for cross-domain heterogeneous unmanned swarms have emerged as a focal point for future unmanned systems. This study analyzes the research status as well as domestic and international development trends of typical application scenarios, including aerial, ground, aquatic, and cross-domain heterogeneous unmanned swarms. Subsequently, it summarizes core technologies of cross-domain heterogeneous unmanned swarms. These technologies involve cross-domain communication and network architectures (including cross-domain swarms wired and wireless communication, and dynamic ad-hoc network architecture), cross-domain collaborative perception and information fusion (including heterogeneous data processing and spatiotemporal registration, and distributed information fusion architecture), cross-domain collaborative decision-making and task planning (including task decomposition and model-based representation, heterogeneous resource allocation and dynamic re-planning, and game-theoretic decision-making and confrontation), cross-domain collaborative control and formation (including cooperative control law design and heterogeneous dynamics, cross-domain formation keeping and formation switching, and swarm consensus and stability analysis), as well as swarm intelligence and emergent behaviors (including behavioral rule modeling and local interaction mechanisms, and swarm cognition, learning, and higher-level emergence). Moreover, major technical bottlenecks are identified, namely constrained cross-domain communication resources, difficulties in information fusion for situational awareness, weak interpretability of cooperative decisions, insufficient stability of heterogeneous dynamic control, and challenges in dynamic regulation of emergent behaviors. Additionally, from the perspectives of individual intelligence enhancement and swarm system evolution, this study highlights the importance of breakthroughs in highly reliable and adaptive cross-domain communication networks, improvement in swarm edge intelligence, in-depth research on task-driven self-organization and emergence mechanisms of swarms, as well as construction of autonomous collaboration and swarm intelligent decision-making systems with learning and evolutionary capabilities. This study aims to provide solutions for building a highly autonomous and standardized cross-domain intelligent collaborative system, and contribute to the theoretical development, technological breakthroughs, and engineering implementation in future unmanned systems.