The present invention provides a recombinant fusion protein containing a first extracellular Ig-like domain of a signal-regulator protein alpha (SIRPα), linked to an Fc fragment of a human IgG1. The present invention also provides a polynucleotide encoding the recombinant fusion protein, an expression vector containing the polynucleotide, a method for producing the recombinant protein and a method for treating a disease caused by over expression of CD47.