A vector system for expressing a soluble protein with high efficiency is provided to rapidly verify the increase of solubility of a target protein, and select a recombinant showing optimal expression efficiency and solubility. The vector system for expressing the soluble protein comprises (a) promoter, (b) a polynucleotide encoding a fusion partner for increasing solubility of the target protein, coupled with histidine Taq, (c) a recognition sequence of a TEV(tobacco etch virus) protein decomposing enzyme, (d) a polynucleotide encoding a linker consisting of 2-10 amino acids, and (e) a multicloning site, wherein the fusion partner is thioredoxin(Trx), N-utilization substance protein A(NusA), maltose binding protein(MBP) or glutathione-S-transferase(GST). The method for constructing the optimal expression system of the target protein comprises the steps of: amplifying the nucleotide sequence encoding the target protein by PCR; introducing the PCR product into the multicloning site of two or more expression vec
