A scheme for all-optical OR gate is proposed based on teraherz optical asymmetric demultiplexer (TOAD). The feasibility of this scheme is theoretically analyzed with the principle of TOAD. Based on this, all-optical OR gate operation at 10 Gb/s is successfully demonstrated. Two data signals coded 1100 and 0110 are used in the experiment, giving chance to demonstrate all of the possibilities of OR gate operation. The successful demonstration of such kinds of codes also shows the potential of this scheme to process OR gate operation on data with arbitrary codes or data of pseudo-random bit streams (PRBS). For the influence of the gain recovery time of SOA, optimising method is proposed. Analysis shows that with this scheme, ultrafast and high extinction ratio OR gate operation can be performed.