The invention discloses a straw crushing and returning machine used for soil improvement in saline-alkali soil. The machine comprises a machine frame, a power device, a driving wheel and an operatinghandle, a connecting place of the operating handle and the machine frame is provided with a handle elevation adjusting device, the rear end of the machine frame is detachably connected with a crushingframe in a hanging manner, the crushing frame is provided with a ground wheel and a crushing box, at least two straw crushing devices are installed in the crushing box in an arranging manner, the rear end of the crushing box is provided with broken straw outlets and fixing sleeves, and a rotary tillage device is movably installed in each fixing sleeve. According to the machine provided by the invention, an elevation angle of the operating handle can be adjusted by utilizing the handle elevation adjusting device, straw is crushed in the crushing box by using the straw crushing devices, the crushed straw is scattered out through the broken straw outlets, and the rotary tillage devices can perform rotary tillage with different depths on the saline-alkali soil, the broken straw is directly and uniformly distributed in soil of rotary tillage after being output, a part of the broken straw enters a deep layer of the soil along with rotary tillage cutters, the crushed straw is uniformly distributed to the soil of the saline-alkali soil with different depths, and soil improvement effects of a saline-alkali soil layer are consistent.