Modulating the helicity of self-assemblies of conjugated molecules is important for their application in chiral electronics. In this communication, solvent effect has been investigated on how to modulate the helicity of supramolecular assemblies of sugar-substituted perylenediimide (PTCDI-BAG) by using UV-Vis, circular dichroism spectroscopy and transmission electron microscopy. Left-handed helical nanowires are obtained in the mixed solvent system of both N,N-dimethylformamide/ethanol (DMF/ethanol) and N,N-dimethylacetamide/ethanol (DMAC/ethanol). As changing the solvents into dimethyl sulfoxide/ethanol (DMSO/ethanol), ethylene glycol/ethanol (EG/ethanol), or N-methyl-2-pyrrolidone/ethanol (NMP/ethanol), only right-handed heical nanowires are observed. The chirality of supramolecular structures can be tuned by the controlling of the polarity of the solvents. A theoretical calculation is carried out to explain the chiral optical inversion phenomena of PTCDI-BAG aggregates in different solvents, which reveals that reversed CD spectra is due to the difference of clockwise and anticlockwise rotation of the dimer.