In response to host CRISPR-Cas attack, bacteriophages and archaeal viruses evolved a range of diverse anti-CRISPR (Acr) proteins to inhibit host immunity. Our recent research has focused on inhibitory mechanisms employed by archaeal viruses. I will present our recent data on a type III CRISPR-Cas inhibitor, AcrIIIB2. This viral protein binds to CRISPR-Cas type III effector complex and inhibit the turnover of the complex so that continuous activation of enzymatic activities (e.g. ssDNase, cOA synthesis) can not be achieved. The data not only shed light on how a virus inhibit type III CRISPR immunity, but also point out the importance of complex turnover for type III CRISPR-Cas immunity.