In this study, a new design of impact-jet nested double-layer microchannel heat sinks with streaming block is described using 3D printing technologies for improving thermal performance. Both simulation and experiments show that the novel structure arrays improve the thermal characteristics when a streaming block is added to the channel compared with the ones without streaming blocks. The results of five 3D-printed test samples made by Selective Laser Melting method are confirmed by numerical simulations with laminar flow and experimental measurements. Under the same conditions, adding a streaming block to the lower channel significantly increases the thermal performance factor by 7 % on average. Heat transfer enhancement is very pronounced in both the streaming lower block and streaming upper block, as shown by the experimental research and numerical simulation. Additionally, among the five models, the impact-jet nested double-layer microchannel heat sinks with streaming upper block equaling 0.3 mm height shows the best overall thermal performance factor. In the case of Reynolds number equaling 580.4, the overall thermal performance factor of impact-jet nested double-layer microchannel heat sinks with streaming upper block equaling 0.3 mm height is 1.5807. The results indicate that the impact-jet nested double-layer microchannel heat sinks with streaming upper block equaling 0.3 mm height can achieve good heat dissipation with minimal pressure drop loss. The novelty of the work is to combine the advantages of double-layer microchannel, impact-jet nested structure and streaming block to enhance the overall thermal performance for extending the full lifecycle of micro electronic devices.