A data processing method and system provided in this disclosure can perform encoding spectrum modulation on original data, so that an amplitude of an original frame in a selected region is smoothly decreased, thereby reducing an amount of data information and improving data compression efficiency; during decompressing compressed data, decoding spectrum modulation is performed on the compressed data by using parameters corresponding to the encoding spectrum modulation, subtraction is performed between the compressed data and the data that has undergone the decoding spectrum modulation to obtain boundary information, and the boundary information is then superimposed on the compressed data, so that an amplitude of decompressed data is restored or enhanced in the selected region. The decoding spectrum modulation may effectively avoid a ringing effect. The method and system can improve the data compression efficiency, and improve transmission efficiency, while improving definition of the decompressed data.