An available model for calculation of broad-band adiabatic flipper of polarized neutrons is suggested. This model of the sine-cosine modulation of an effective field enables one to optimize and to simplify calculation for constructing the flipper. Functional relation between spin-flip probability and main parameters of the device such as length of flipper, neutron wavelength and both form and size of magnetic fields have been found. The test of the flippers constructed on the base of the model has been successfully carried out.