A method for realizing adaptive quantization in image encoding and dequantization in image decoding is disclosed. In the adaptive quantization method, an image to be encoded is divided into one or more blocks, and each block is transformed to obtain one or more transform coefficients, the method comprising: acquiring parameter information of neighbor blocks of a current block; determining a quantization mode for the current block according to the parameter information of the neighbor blocks; and quantizing transform coefficients of the current block in the determined quantization mode. The quantization mode includes at least one of quantization matrix, quantization parameter and quantization step.