Abstract: The theoretical basis and experimental methods for measuring the frequency,amplitude and phase of sinusoidal alternating current using a pump-probe rubidium atomic magnetometer are reported.The physical law of the interaction between the radio frequency field and the atomic magnetic moment is classically described by using a rotating coordinate system,and the signal expression of the atomic magnetometer is given in the laboratory coordinate system.The radio-frequency magnetic field at the location of the rubidium vapor cell is generated by a Helmholtz coil carrying the sinusoidal alternating current,and the parameters of the sinusoidal alternating current in Helmholtz coil can be obtained by fitting the magnetic resonance curves.Ten repeated measured curves are fitted,and the relative standard deviations of the frequency,amplitude and phase of the sinusoidal alternating current reach 5.4×10^-7,2.3×10^-5 and 3×10^-3,respectively.The relative standard deviation of the frequency is related to the resolution of current source,which is used to generate the background magnetic field.The study is helpful for people to deepen the understanding of the classical physical picture of the two-level magnetic resonance transition and to measure the parameters of sinusoidal alternating current.