The invention discloses a single-engine washing and sweeping vehicle. The single-engine washing and sweeping vehicle comprises a chassis, a full-power power takeoff, an auxiliary gearbox, an operation walking system, an auxiliary vehicle frame, a transfer case, a fan assembly, an oil pump assembly, a high-pressure water pump assembly, a box body, a disc brush, a suction opening and the other operation devices. The full-power power takeoff, the auxiliary gearbox and the operation walking system are arranged in a chassis transmission system, the transfer case, the operation devices and the box body are arranged on the auxiliary vehicle frame, power of a chassis engine is driven to the transfer case through the full-power power takeoff and a transmission shaft, three output openings of the transfer case drive the various operation devices respectively, and the operation walking system comprises a walking variable pump, a walking motor and an accessory device. In the working process, the power takeoff of the chassis gearbox drives the variable pump, and a closed type system is formed by the variable pump and the walking motor. The chassis engine is utilized for achieving chassis walking and driving in the driving and operation process of the washing and sweeping vehicle, and high-speed stable rotating speed of the operation device and low-speed and variable-speed walking control of the chassis are ensured.