[en] Described is a method of calibration and preparing U²³⁵ two side targets, used in experiments on precise measurements of fission cross-sections. A method of multylayer painting is used for preparation of U²³⁵ targets on a 25 mm thick aluminium substrate of 160 mm in diameter. The investigated isotope in the form of a specially prepared solution is put on a substrate by a brush and then is annealed at 550 deg C. The procedure is repeated until obtaining the layer of definite thickness. The uranium concentration in the solution must not surpass 20 mg/ml. The U²³⁵ two side targets with the diameter of active layers of 140 mm were prepared using the described method. The target calibration according to the number of nuclei was carried out in 3 ways: by weight, α-particle counting in a 2π counter and α-particle counting in a small solid angle. The measurement result analysis of the number of U²³⁵ nuclei on the prepared targets conducted by 3 different methods showed, that each of the three calibration methods permits to determine the uranium layer weight on the target with an error not worse than 1% at the 70% c.l