A Hamming neural network circuit which can be programmed and expanded is disclosed. The Hamming neural network includes an I/O circuit for inputting and outputting a plurality of standard patterns. A bi-directional transmission gate array is connected to the I/O circuit and controlled by a programming signal for transmitting the standard patterns. A plurality of standard pattern memory units is connected to the bi-directional transmission gate array for storing the plurality of standard patterns respectively. An address decoder is connected to the plurality of standard pattern memory units for addressing one of the plurality of standard pattern memory units. A plurality of pattern matching calculation circuit units are respectively connected to the plurality of standard pattern memory units for generating a plurality of matching rates between a to-be-recognized pattern and the plurality of standard patterns. An expandable matching rate comparing circuit is provided for comparing and sorting said plurality of matching rates.