G-induced loss of consciousness (G-LOC) means that when the pilot is exposed to positive acceleration (+Gz), the blood is rapidly transferred to the lower body due to inertial forces, results in acute cerebral ischemic and hypoxia and loss of consciousness. G-LOC is highly likely to cause catastrophic consequences. Currently, there is no effective method to avoid G-LOC. The fundamental strategy to solve this problem is to warn pilots of the potential danger of G-LOC by real-time physiological monitoring and to alert them to take timely measures. Advances in technologies of wireless sensing and artificial intelligence have made dynamic and accurate measurement possible. By reviewing the progress of sensitive physiological indexes during high +GZ exposure, this paper analyzes the characteristics and significance of head level hemodynamics, electroencephalogram, cerebral oxygen metabolism, electrocardiogram and electromyogram before and after the occurrence of G-LOC, summarizing the existing alerting technologies and their deficiencies. It is concluded that multi-index physiological monitoring combined with pilot physical signs and aircraft maneuvering status for a comprehensive judgment is a future way for solving G-LOC early warning issues.