A Brisbane man accused of claiming to be an ASIO spy in order to rape a child and commit a large number of other child sexual offences over three years, has been released on bail.

The 20-year-old — who cannot be named for legal reasons — is facing more than 80 charges, including more than 15 counts of indecently treating a child, sexual assault, and several child-exploitation charges.

Police will allege he preyed on more than 15 "vulnerable" children, between the ages of 13 and 16 since 2015, gaining their friendship by telling them he was recruiting young spy operatives.

He is also accused of supplying some of his victims with cannabis and alcohol, letting them drive his car and threatening them.

Court documents said he issued a death threat to one of his victims, saying he would run him over with his car.

A judge granted bail under a long list of strict conditions.

It included wearing an electronic monitoring device and having a 24-hour curfew, which means he cannot leave his house unless in the presence of his mother or an approved medical practitioner.

He must also have no contact with anyone under the age of 18, any witnesses, and cannot drive any vehicles.

When granting bail, Magistrate Judith Daley warned the man his alleged offending was serious and he should not breach any condition.

"These are very strict conditions because they are very serious charges," she said.

The matter will return to court in December.