The utility model provides a system for increasing propylene yield, which comprises an MTP reactor provided with a side material inlet, a top material inlet and a product outlet, the side material inlet is connected with a side feeding pipeline, and the top material inlet is connected with a top feeding pipeline; the mixed alcohol tank is respectively communicated with the first mixed alcohol output pipe and the second mixed alcohol output pipe; the DME separation tank is provided with a gas-phase component outlet and a liquid-phase component outlet, the gas-phase component outlet is connectedwith a gas-phase output pipeline, the liquid-phase component outlet is connected with a liquid-phase output pipeline, and the gas-phase component outlet, the liquid-phase component outlet and the liquid-phase component outlet are all communicated with the side line feeding pipeline; the heating furnace is used for receiving and heating DME materials, circulating hydrocarbon and mixed alcohol conveyed by a second mixed alcohol output pipe, and a material outlet of the heating furnace is connected with the top feeding pipeline; and the nitrogen purging device is communicated with the side linefeeding pipeline. The system can effectively prevent mixed alcohol from remaining on the side line feeding pipeline after the MTP reactor is off line so as to avoid the coking phenomenon.