An interface card and a computer motherboard which are used in a horizontal adaptation include a motherboard on which is configured with at least two sets of first slots; and at least one interface card, a side of which is provided with at least two sets of adapting parts being correspondingly plugged into the aforementioned two sets of first slots, and one set of the adapting part on which is connected with a circuit of the interface card. By assembling the two sets of first slots on the motherboard correspondingly with the two sets of adapting parts on the interface card, the interface card can be firmly positioned on the motherboard. The adapting part is connected with the circuit of interface card and corresponding plugged into the first slot, such that the interface card can be electrically conducted with the motherboard thereby exchanging and processing messages.