Abstract Materials with ultra-narrowband light transparent window are desirable for applications in optoelectronics. Due to the intrinsic loss in the traditional metallic nanostructures, the plasmonic or electromagnetically induced light transparent spectrum is with a typically broad bandwidth. In this work, a novel strategy for achieving ultra-narrowband optical transparent window is theoretically proposed and demonstrated based on the dielectric dimer resonators metamolecule array. Owing to the electromagnetic resonant coupling in this lossless all-dielectric metamolecule, a transparent window with the bandwidth down to nanometer scale and the spectral slope up to 71%/nm is achieved. The obtained optical properties can be manipulated in the spectral range by adjusting the structural parameters and dielectric permittivity. These findings pave a new way for sharp narrowband transparent window with potential applications in filtering, optical manipulation, etc.