Abstract: Objective　To understand the relationship between mycoplasm load in bronchoalveolar lavage fluid (BALF) with the status of Th1/Th2 immune response in children with Mycoplasma pneumoniae pneumonia (MPP). Methods　The levels of IL-4, IFN, IL-8 , TNF-α in BLAF and total IgE, ECP in serum from 90 children with MPP were measured by ELISA.MP DNA in BALF was detected quantitatively by fluorescent real-time PCR. Children with MPP (n=90) were divided into two groups of low MP-DNA load (n=24) and high MP-DNA load (n=26) according to the copies of MP DNA in BALF. The cytokines in BALF, and total IgE and ECP in serum were compared between the two groups. The relationship between the levels of cytokines in BLAF and the copies was evaluated. Results　The levels of IL-4 and the IL-4/IFN ratio in BALF from the high DNA-load group were significantly higher than that of the low group (t=4.280, 2.076, all P<0.05). The level of IL-4 was significantly correlated with the copies of MP-DNA in BALF from children with MPP (r=0.509, P<0.05). The percentage of total IgE and ECP positive result in serum from the high DNA-load group is higher than that of the low group. (χ2=24.638, 6.392, all P<0.05). Conclusion 　Infection with high-load MP in children may cause the imbalance of Th1/Th2. And the Th2 cytokines response seems predominant.