The present disclosure discloses a mask S-box, a block ciphers algorithm unit, a device and a corresponding construction method. The mask S-box includes an input module, an address mapping processing module, and an output module. The input module receives a random number and an input data which is masked by the random number and uses the random number and the input data as two inputs of the mask S-box. The address mapping processing module performs one-to-one mapping on the two inputs and the corresponding memory address of the mask S-box. The output module linearly processes the random number by using a linear function to obtain the linearly converted random number, which is used as one output of the mask S-box. The memory address obtained by using the linearly converted random number to mask the output of the original S-box is used as the other output of the mask S-box.