In this article we analyzed the pathogenic characteristics and treatment strategies of COVID-19 infection complicated with underlying diseases in the elderly by introducing 2 proved cases. Elderly patients with COVID-19 are identified with pathogenesis of dampness， heat， toxicity， stasis and deficiency， and the pathogenesis of deficiency and stasis is the most prominent. The deficiency of vital qi exists throughout the disease course. Traditional Chinese medicine （TCM） treatment principles for elderly patients with COVID-19 include： early intervention， integration of pathogen-eliminating and vital-qi strengthening， and application of treatment methods to guide pathogens out， for instance， the method of dispersing lungs and unblocking bowels， the method of clearing heat and resolving dampness， and the method of supplementing and strengthening vital qi， etc. Additionally， attention should be paid to the treatment of underlying diseases. Treat both the newly contracted infection and persistent diseases， but one need to distinguish the priorities， and treat accordingly and flexibly.