A leakage-current start-up reference circuit is provided which includes a reference circuit unit, a trigger unit, a leakage-current generator and a disable control unit. The trigger unit includes a first transistor. The drain terminal of the trigger unit is connected to a start-up terminal of the reference circuit unit. The leakage-current generator includes a second transistor which is a gate-drain-tied transistor. The disable control unit includes a third transistor. The gate terminal of the disable control unit is connected to a control terminal of the reference circuit unit. The drain terminal of the leakage-current generator, the gate terminal of the trigger unit and the drain terminal of the disable control unit are joined at a node. The reference circuit unit is started up by the trigger unit to generate a reference current. A leakage-current start-up reference circuit having a current mirror is also provided.