The present invention relates to a liquid formulation of long-acting insulin conjugate, comprising a pharmaceutically effective amount of a long-acting insulin conjugate, wherein a physiologically active peptide, which is an insulin, is linked to an immunoglobulin Fc region； and an albumin-free stabilizer, wherein the stabilizer comprises a buffer, a sugar alcohol, a non-ionic surfactant, and an isotonic agent, and a method for preparing the formulation. For preventing microbial contamination in multiple uses, a preservative can be added to the formulation. The liquid formulation of the present invention does not comprise a human serum albumin and potentially hazardous factors to body, and thus it has excellent storage stability for insulin conjugate without a risk of viral infection.
