This disclosure provides a content addressable memory which includes: a data memory cell for storing a data bit; a mask memory cell for storing a mask bit; and a comparing and readout unit connected to at least one read word line for receiving at least one read word signal, connected to at least one function bit line for receiving a search bit signal, and connected to the data memory cell and the mask memory cell for receiving the data bit and the mask bit; wherein the data memory cell is connected to a data-use write word line for receiving a data-use write word signal, the mask memory cell is connected to a mask-use write word line for receiving a mask-use write word signal, so as to decide whether a write bit signal can be written into the data bit and the mask bit through a pair of write bit lines.