Application of chemical/biological agents in terrorism and unmilitary fields induce serious impact to the public safety. Principles of laser warning and detection technology for chemical/biological agents based on Mie scattering signals, Rayleigh scattering signals, Raman scattering signals, absorption signals and laser induced fluorescence signals are described. The key technologies in the laser warning and detection system are analyzed, the laser warning and detection technology development profiles in the United States, Russia, German and France are introduced.