[en] We present a method to construct the wide-band achromatic metalens in full visible waveband. The metalens is accomplished via arrayed rectangular dielectric nanoblocks which can manipulate the electromagnetic waves to support focusing function. The research results indicate that the dielectric nanoblocks with different widths can achieve the phase shift, in addition, the lengths of the dielectric nanoblock provide an extra degree of freedom for realizing the control of the wavefront. Therefore, the double regulation functions of widths and lengths can realize dispersion compensation. Finally, we design and simulate an achromatic metalens through combining dielectric nanoblocks with varied widths and lengths, which can achieve wide-band achromatic focusing in the spectral range from 0.4 µ m to 0.8 µ m with high diffraction efficiency (about 69%–84%). The method may be applied as an effective solution of wide-band light manipulation in integrated optical systems. (paper)