The complement system is an important part of innate immunity. Through complement-dependent cytotoxicity (CDC), it plays an important role in the clearance of invading pathogens but also cancerous host cells. Therapy with anti-CD20 monoclonal antibodies (mAbs), for example, rituximab and ofatumumab, is a well-established treatment for lymphoid malignancies, and CDC is one of the main mechanisms underlying their anti-cancer activity. However, there are still some issues with the clinical application of anti-CD20 antibodies. On the one hand, anti-CD20 can cause some clinical side effects; on the other hand, anti-CD20 has low potency in some patients, and increasing the dosage does not enhance its effectiveness in these patients. Previous studies have reported that a gain-of-function in a certain complement component can boost the cytolytic activity of anti-CD20 mAbs. Through reviewing the literature on complement system control and anti-CD20 mAbs, this article aims to provide a thorough understanding of the potential of targeting complement components in lymphoma therapy.