A proportion adjustable single-photon beam splitter based on cold atom storage includes a two-dimensional magneto-optical trap for receiving a first optical signal to be split; and a coupling beam. The coupling beam is incident at a certain angle with the first optical signal to the two-dimensional magneto-optical trap. The storage time of the two-dimensional magneto-optical trap 1 can be adjusted by controlling the switching time of the coupling beam, and then adjusting a proportion of a photon number of a storage part and a photon number of a leakage part of the first optical signal. A splitting proportion may also be adjusted by controlling an optical depth of the alkali metal atomic group trapped in the two-dimensional magneto-optical trap.