An apparatus for mixing transmission and separation of hydrogen gas and natural gas recovered based on pressure energy, comprising a hydrogen compressed natural gas pipeline, a pressure energy recovery system, a separation system and a pressure boosting system; wherein the pressure energy recovery system is composed of an expander, a first natural gas compressor, and a first hydrogen gas compressor; the expander being provided thereon with an air inlet, an air outlet, a water inlet and a water outlet; the first natural gas compressor being provided thereon with an air inlet, an air outlet, a water inlet and a water outlet; the first hydrogen gas compressor being provided thereon with an air inlet, an air outlet, a water inlet and a water outlet; the expander being assembled with an auxiliary motor, and the first natural gas compressor being connected in parallel with the first hydrogen gas compressor, and being assembled with the auxiliary motor; the separation system is composed of a separation apparatus, a first hydrogen gas buffer tank, and a first natural gas buffer tank; the separation apparatus being provided with an air inlet, a hydrogen gas outlet, and a natural gas outlet; the first hydrogen gas buffer tank being provided thereon with an air inlet and an air outlet, the first natural gas buffer tank being provided thereon with an air inlet and an air outlet; the pressure boosting system is composed of a second natural gas compressor and a second hydrogen gas compressor; the second natural gas compressor being provided thereon with an air inlet and an air outlet, and the second hydrogen gas compressor being provided thereon with an air inlet and an air outlet; the air outlet of the hydrogen compressed natural gas pipeline is communicated with an inlet of a general buffer tank, an outlet of the general buffer tank is communicated with the air inlet of the expander, and the air outlet of the expander is communicated with the air inlet of the separation apparatus, the hydrogen gas outlet of the separation apparatus is communicated with the air inlet of the first hydrogen gas buffer tank, the natural gas outlet of the separation apparatus is communicated with the air inlet of the first natural gas buffer tank; the air outlet of the first hydrogen gas buffer tank is communicated with the air inlet of the first hydrogen gas compressor, and the air outlet of the first natural gas buffer tank is communicated with the air inlet of the first natural gas compressor; the air outlet of the first hydrogen gas compressor is communicated with the air inlet of the second hydrogen gas buffer tank, the air outlet of the first natural gas compressor is communicated with the air inlet of the second natural gas buffer tank; the air outlet of the second hydrogen gas buffer tank is communicated with the air inlet of the second hydrogen gas compressor; the air outlet of the second natural gas buffer tank is communicated with the air inlet of the second natural gas compressor; the air outlet of the second hydrogen gas compressor is communicated with a hydrogen gas user or the hydrogen compressed natural gas pipeline; the air outlet of the second natural gas compressor is communicated with the hydrogen compressed natural gas pipeline, or a natural gas user end.