NOVELTY - Preparing fuel by sludge and straw, comprises (i) introducing hydrophobic wet sludge and straw into a steam explosion reactor; (ii) closing the inlet opening before introducing the gas into a tank body, pressurizing the tank body at the steam explosion pressure when the raw material is heated at the steam explosion temperature, quickly relieving the pressure and crushing biomass and sludge cell, then uniformly mixing the raw materials; (iii) dehydrating the exploded mixture in a dehydrator; and (iv) molding the hydrophobic mixture to obtain the sludge synthesized fuel.    USE - The method is useful for preparing fuel by sludge and straw.    DETAILED DESCRIPTION - Preparing fuel by sludge and straw, comprises (i) introducing hydrophobic wet sludge with less than 85% of water content and straw in the ratio of 20:1-20:5 in a steam explosion reactor; (ii) closing the inlet opening before introducing the gas into a tank body, pressurizing the tank body at the steam explosion pressure when the raw material is heated at the steam explosion temperature, quickly relieving the pressure within 10-300 seconds and crushing biomass and sludge cell, then uniformly mixing the raw materials; (iii) dehydrating the exploded mixture in a dehydrator; and (iv) molding the hydrophobic mixture to obtain the sludge synthesized fuel. An INDEPENDENT CLAIM is also included for a device for preparing the sludge synthesized fuel, comprising a feeder (1), a steam explosion reactor (2), a buffer kettle (3), a dehydrator (4) and a molding machine (5). The outlet of the feeder is connected to an inlet of the steam explosion reactor, and the outlet of the steam explosion reactor is connected to an inlet of the buffer kettle. The outlet of the buffer kettle is connected to an inlet of the dehydrator, and the outlet of the dehydrator is connected to an inlet of the molding machine.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the device for preparing the sludge synthesized fuel.    Feeder (1)    Steam explosion reactor (2)    Buffer kettle (3)    Dehydrator (4)    Molding machine (5)