Objective: To obtain recombinant major surface glycoprotein(rMsg)of Pneumocystis jirovecii(Pj) and survey anti-Pj rMsg IgG and IgM antibodies using enzyme-linked immunosorbent assay (ELISA) among randomly selected sera from Beijing local children under 14 years of age. Methods: ELISA method were established to detect anti-Pj rMsg IgG and IgM antibodies. We randomly selected sera of 201 cases who were under 14 years of age were screened. Results: There were 78 cases in the age group of 1 day to 30 days, 33 cases in the group of 1 month to 12 months, and 90 cases in the group of 1 year to 14 years. The positive rates of anti-Pj rMsg IgG antibody in these three age groups were 10.3%(8/78), 21.2%(7/33), and 41.1%(37/90)respectively(χ²=21.190, P=0.000). The positive rates of anti-Pj rMsg IgM antibody were 6.4%(5/78), 39.4%(13/33), and 76.7%(69/90)respectively(χ²=84.260, P=0.000). The overall positive rates of anti-Pj rMsg IgG and IgM antibodies were 25.9%(52/201)and 43.3%(87/201)respectively(χ²=53.463, P=0.000). Among these, simultaneously IgG positive IgM positive, IgG positive IgM negative, IgG negative IgM positive and IgG negative IgM negative rates were 22.4%(45/201), 3.5%(7/201), 20.9%(42/201), and 53.2%(107/201)respectively. Conclusions The overall serological response rate after Pj exposure, either anti-Pj IgG or IgM antibody positive, was as high as 46.8% in children under 14 years of age in Beijing area. The positive rates of anti-rMsg IgG and IgM antibodies increased with age, with highest rate in age group of more than one years old.