The invention discloses an amplitude estimation method which comprises the following steps of utilizing a convergence factor to confirm an estimated amplitude value and utilizing the estimated amplitude value to estimate the amplitude of an original signal. The amplitude estimation method can dynamically confirm the convergence factor for amplitude estimation. The invention further discloses an interference elimination method of the original signal utilizing the amplitude estimation method. The interference elimination method comprises the following steps that amplitude estimation of all modulation restoring signals is conducted; by means of amplitude estimation results, amplitude regulation of all the modulation restoring signals is conducted; modulation spectrum spread of all the modulation restoring signals after the amplitude regulation is conducted, and multi-site interference signals are obtained; and multipurpose user interference in combined signals is eliminated through the multi-site interference signals. Meanwhile, the invention further discloses an interference elimination device corresponding to the interference elimination method. After the interference elimination method and the interference elimination device are adopted, multi-site interference resistant performance of a multi-user data link system is improved.