Abstract: Rongguan Iron-zinc Mine adopts the transition mining method from open pit to underground.Combining with its engineering geological situation，the paper studied the application of pillarless sublevel caving in this mine，and introduced its structural parameters of the two working benches.Then，some of parameters were optimized，such as lateral opening angle and bench height，by which the bulk rate and the ores loss and dilution rate were lowered，with a better economic benefit obtained.

Key words: Transition from open pit to underground mining, Pillarless sublevel caving method, Parameter optimization, Application study