<p>Astrocytes are the most abundant glial cells in the central nervous system (CNS). Due to their extensive processes, they can interconnect with many neighboring cells and play critical roles in regulating synaptic plasticity, integrating neuronal signals, and maintaining the stability of the extracellular environment. These functions are largely dependent on calcium (Ca²⁺) signaling. In light of these considerations, the powerful functions of Ca²⁺ signaling in astrocytes have been actively studied in recent years. This review summarizes the mechanisms related to Ca²⁺ waves in astrocytes as well as their physiological and pathological functions mediated by various calcium signaling, the characteristics of calcium waves, and the role of Ca²⁺ in astrocytes in the CNS injuries of spinal cord injury (SCI) and traumatic brain injury (TBI) recently. However, inhibited L-type voltage-gated Ca²⁺ channels (LTCCs) activity and reduced Ca²⁺ concentration result in an opposite phenomenon that promoting or reducing astrogliosis. This highlights the importance of focusing not only on Ca²⁺ concentration but also on the downstream signaling pathways initiated by Ca²⁺. Therefore, we summarize diverse signaling pathways in various physiological and pathological contexts.</p>