Coherent control of self-contained quantum systems offers the possibility to fabricate smallest thermal transistors. The steady coherence created by the delocalization of electronic excited states arouses nonlinear heat transports in non-equilibrium environment. Applying this result to a three-level quantum system, we show that quantum coherence gives rise to negative differential thermal resistances, making the thermal transistor suitable for thermal amplification. The results demonstrate that quantum coherence facilitates efficient thermal signal processing and can open a new field in the application of quantum thermal management devices. (C) 2021 Elsevier B.V. All rights reserved.