Abstract: Objective: To investigate the current status of insulin usage and its related problems among firstly diagnosed diabetic patients in Department of Cardiology and to provide professional and educational guidance to the patients. Methods: We randomly selected 192 diabetic patients at the clinic from August 2014 to August 2015.The sample included 84 patients who were firstly diagnosed diabetes in Department of Cardiology and 108 patients who were firstly diagnosed diabetes in Department of Endocrinology. We investigated and compared the current status of insulin usage in the two Departments. Results: The percentage of injection dose as prescription are as follows: Department of Endocrinology group VS Department of Cardiology group, 76.9% VS 64.3% (P=0.049); the percentage of correct injection site: Department of Endocrinology group VS Department of Cardiology group, 94.4% VS 84.5% (P=0.023); the percentage of injection after sterilization area is dried: Department of Endocrinology group VS Department of Cardiology group, 71.3% VS 53.6% (P=0.012); the percentage of exhausting before injection: Department of Endocrinology group VS Department of Cardiology group 73.1% VS 47.6% (P<0.001); the percentage of the needle stayed more than10 seconds after injection: Department of Endocrinology group VS Department of Cardiology group, 96.3% VS 84.5% (P=0.004); the percentage of taking off the needle from the pen after each injection: Department of Endocrinology group VS Department of Cardiology group, 37.0% VS 22.6% (P=0.032). Conclusion: Patients who were first diagnosed of diabetes in Department of Cardiology received insufficient guidance of correct methods in insulin injection, so they need professional guidance about using insulin from medical professionals.