A method of preparing a heparin-conjugated fibrin gel is provided, which includes activating heparin, conjugating the activated heparin with fibrinogen to prepare heparin-conjugated fibrinogen, mixing free fibrinogen with the heparin-conjugated fibrinogen to prepare a fibrinogen mixture, and mixing thrombin with the fibrinogen mixture. In addition, a heparin-conjugated fibrin gel prepared by the above method and a kit for preparing the same are provided. According to the method of preparing the heparin-conjugated fibrin gel, the heparin-conjugated fibrin gel having an affinity for drugs such as growth factors may be easily prepared at low costs, and can also be used as a therapeutic drug excellently effective on generation of tissues such as bones, skin, blood vessels, cartilages, etc. by sustainably releasing drugs such as growth factors to a local site for a long period of time through injection into a human body.