The invention relates to a light crossing matrix in an optical fiber channel switch and an operation method. The light crossing matrix comprises a matrix controller and n<2> identical wavelength selection switches, wherein n is an integer ranging from two to nine, each wavelength selection switch is provided with 1+n<2> add-drop multiplexing ports which include an input port, an output port and n<2>-1 interconnection ports, and the wavelength selection switches are in butt joint in a one-to-one mode. The matrix controller is connected with the wavelength selection switches so as to control the ports to be opened and closed, and the light crossing matrix in the n<2> directions is formed. A line card controller is in communication connection with the matrix controller and the wavelength selection switches for data transmission. The operation method includes the steps that the matrix controller checks the states of the correlated ports according to the direction of a data pack; if the states of the correlated ports are idle, a communication link is built; if the states of the correlated ports are busy, priorities are compared, the port with a low priority is broadcasted and the operation is neglected; if the priority is high, the current operation is interrupted, a communication link is built and the communication link is disassembled after transmission is finished. The light crossing matrix and the operation method reduce interference, improve efficiency and facilitate upgrading for processing and exchanging of light signals.