This is a multicenter, non-randomized, open-label, phase I/II study in children with ACH. This study will start with a dose escalation of ABSK061 in children with ACH to evaluate the safety, tolerability, PK, and efficacy. The RDE confirmation part will evaluate the safety and efficacy of ABSK061 at the recommended doses for expansion (RDEs) in children with ACH. All patients enrolled in the dose escalation part and RDE confirmation part can enter the extended treatment period to further evaluate the long-term safety, tolerability, and long-term efficacy of ABSK061 in children with ACH.