Abstract: The purpose of the work is to research the planar source of ¹⁴C with large size by the absorbability of the anodizing membrane. The adsorption of ¹⁴C on the anodizing membrane with thickness of 4 to 12 μm were investigated. The adsorption of ¹⁴C and the uniformity of the planar source were investigated on the volume of ¹⁴C solution. The specific activity of ¹⁴C was investigated on adsorption of ¹⁴C. The fastness, the uniformity and the surface emission rate of the planar source of ¹⁴C were measured. The result shows that the uniformity of the planar source (100 mm×150 mm) of¹⁴C is precede 10%. The plateau length is 400 V, the slope of the plateau is 0.3% per 100 V. The threshold correction is 0.2%. The uncertainty of ¹⁴C source measurement is 2% (k=2). The technical parameters of the developed plane source ¹⁴C can meet the requirements of relevant standards.