Objective To investigate the exposure difference of different dosage forms of mycophenolic acid (MPA) between children aged ≤12 and > 12 years old after kidney transplantation. Methods Clinical data of 73 children undergoing kidney transplantation from donation after cardiac death (DCD) were retrospectively analyzed. Postoperative immunosuppressive regimen was MPA+ tacrolimus+glucocorticoid. According to different dosage forms of MPA, all recipients were divided into group A (n=37, mycophenolate mofetil capsules), group B (n=28, enteric-coated mycophenolate sodium) and group C (n=8, mycophenolate mofetil dispersible tablets). All children were divided into ≤12 and > 12 years old groups according to the age of kidney transplantation. The daily dosage of different dosage forms was calculated. The blood concentration (C) of MPA and the area under the curve (AUC) were detected by enzyme-multiplied immunoassay technique. The MPA blood concentration was statistically compared between two age groups at different time points. The recovery of renal function and postoperative complications were assessed. Results No significant differences were observed in the dosage and blood concentration of drug at different time points among groups A, B and C (all P > 0.05). The MPA-C4 h and AUC in the ≤12 years old group were significantly higher than those in the > 12 years old group (both P < 0.05). In group B, the MPA-C4 h of children aged ≤12 years old was significantly higher compared with that in those aged > 12 years old (P=0.016). The MPA-C4 h of children aged ≤12 years old in group B was higher than those in group A and group C, but the differences were not statistically significant (P=0.080). There was no significant difference in the incidence of acute rejection and infection among three groups (both P > 0.05). Conclusions Children of different ages who are given with different dosage forms of MPA after kidney transplantation obtain different exposure rates. The exposure rate of kidney transplant recipients aged ≤12 years old tends to be higher than that of their counterparts aged > 12 years old, mainly seen in the recipients treated with enteric-coated mycophenolate sodium. Therefore, it is necessary to monitor the exposure level of MPA, which provides significant guidance for adjusting the drug dosage of different dosage forms.