The measurement of infrared radiation characteristics of ship and coastal targets is among the most important components of target infrared radiation characteristic measurements. The traditional ground model corrects only the atmospheric transmittance, so the measurement error of the target cannot meet the measurement requirements of infrared radiation characteristics. This study proposes a method that measures the target radiation characteristics based on reference sources to maximize the measurement accuracy. Experiments for infrared radiation characteristic measurements are conducted near the coast by using a long-wavelength infrared radiation characteristic measurement system with an aperture of 600 mm. Experimental results confirm that the proposed method reduces the radiation measurement error to 4.31%, which is higher than the inversion accuracy of the traditional method.