OBJECTIVE： To compare clinical efficacy， ADR and cost of moxifloxacin alone vs. piperacillin/tazobactam combined with azithromycin in the treatment of elderly community acquired pneumonia （CAP）. METHODS： In retrospective study，  60 elderly CAP patients were selected from respiratory department of a third grade Class A hospital during Oct. 2015-Apr. 2016， and then divided into group A， B with 30 cases in each group according to the medication regimen. Group A was given Moxifloxacin hydrochloride and sodium chloride injection 250 mL， ivgtt， qd； group B was given Azithromycin latobionate for injection 0.50 g， ivgtt， qd+Piperacillin sodium and tazobactam sodium for injection 3.375 g， ivgtt， q8 h. Both groups were treated for 10 d. Clinical efficacy， bacteriological efficacy and the occurrence of ADR were compared between 2 groups. The economics of 2 therapy plans were evaluated. RESULTS： Total response rates of group A and B were 90.00％ and 93.33％； bacterial clearance rates were 85.00％ and 86.36％； the incidence of ADR were 3.33％ and 6.67％， without statistical significance （P＞0.05）. Minimum cost analysis was adopted for economic evaluation； treatment cost of group A was 16 646.51 yuan， and that of group B was 19 605.74 yuan； the cost of group A was lower than group B. The results of minimum cost analysis were supported by sensitivity analysis. CONCLUSIONS： For empiric treatment of antibiotics in elderly CAP patients， moxifloxacin alone should be the first choice. The therapy plan is effective， low-cost and safe.