The Alishan Forest Railway from Chiayi is the classic way to arrive and is strongly recommended as an experience in itself. Trains depart Chiayi station (the city rail station, not the HSR station) twice daily in the morning; the journey takes about two and a half hours. Book tickets in advance online, especially for weekends and blossom season — the train fills completely.
The Alishan HSR station is the high-speed rail stop nearest to Chiayi city; from there, a shuttle bus or taxi connects to Chiayi station for the forest railway. By bus, direct express coaches from Chiayi bus station run to Alishan in about two hours via the provincial highway — a faster but less scenic option. Driving your own vehicle is also possible via Route 18; the road is winding but manageable.
The forest railway was partially closed for repairs in recent years; check current operational status before planning a journey by train.