Abstract: Objective　To investigate the probability and timing of childhood Miller-Fisher syndrome (MFS) progressing to Bickerstaff brainstem encephalitis (BBE), classical Guillain-Barre syndrome (GBS), and pharyngeal-cervical-brachial (PCBGBS). Methods　The clinical data of 128 children with confirmed MFS diagnosis were retrospectively analyzed. Results　Among 128 children, 60 cases were simple MFS (ocular muscle paralysis, ataxia, reflexes diminished or disappeared, without limbs weakness and lethargy; laboratory tests suggest cerebrospinal fluid protein-cell separation and/or serum anti-GQ1b antibody positive), 28 cases developed MFS/PCB-GBS (met MFS diagnosis criteria, accompanied by weakness of pharynx, neck and upper limb, weakened or disappeared of upper limb reflex, without weakness of lower limb), 22 cases developed MFS/GBS (met MFS diagnosis criteria, accompanied by weakness of limb), 18 cases developed MFS/BBE (met MFS diagnosis criteria, accompanied by lethargy, pyramidal tract positive). There were no differences in the age at onset, the interval from onset to the start of the treatment, Hughes functional grading, and the percentage of cases having a history of preceding infections, the rate of positive serum anti-GQ1b antibody, the ratio of albumin cytological dissociation in cerebrospinal fluid among 4 groups (P>0.05). The interval from MFS onset to progression to MFS/PCB-GBS, MFS/GBS, or MFS/BBE was within 10 days. Conclusions　In children with MFS, 50% developed PCB-GBS, GBS, or BBE, which occurred within 10 days after onset. Clinicians should pay attention to the time window and adjust the medicine rationally.