Objective To evaluate the cost and effectiveness for five combination therapy of β-lactam antibiotic with azithromycin in the treatment of mycoplasma pneumonia (MP) complicated with bacterial infection.Methods A retrospective study was conducted to compare the cost and effectiveness of the five regimens.Results The effective rates of group A, B, C, D and E were 97.29%, 100%, 96.55%, 95.65% and 97.36% respectively.The costs were (2 831.13±910.16) yuan,(2 816.31±127.11) yuan,(3 453.29±645.89) yuan,(4 382.42±1484.26) yuan,(3 703.39±124.86) yuan respectively.The cost-effectiveness ratios were (29.10±9.36), (28.16±5.24), (35.77±6.69), (38.04±7.90)and (35.26±10.10)respectively.Conclusion In terms of pharmacoeconomics, the combination of cefpiramide with azithromycin in group B has the lowest cost and cost-effectiveness ratio.This regimen is the most effective and economically favored combination.It is the treatment of first choice for pediatric MP patients complicated with bacterial infection.