Molecular assembly has attracted wide attention in chemistry, condensed physics, molecular electronics, and materials sciences. However, it remains a great challenge to perform post-modulation on the assembled structures without the aid of externally applied fields. Herein, we demonstrate a combined full-weak-bonded interaction and fullerene-derivative strategy and achieve the post-modulation of layer-by-layer assembly with a precision of 5.0 Å. In the absence of external fields, the fullerene derivative exhibits a long-range interaction to boost the modulation of the assembly. Benefiting from that, a catalytic dose of fullerene derivative is able to modulate a large area of assembly, reminiscent of the catalyst in chemical reactions. This work provides an efficient and flexible approach for the catalysis and precise modulation of molecular assembly.