The invention provides a harmless treatment environment-friendly device for crop straws, and belongs to the technical field of crop straw environment-friendly treatment. The harmless treatment environment-friendly device comprises a treatment machine body, a primary crushing chamber, a secondary crushing chamber, a waste gas treatment chamber, a waste gas purifying chamber and a water storage tank. According to the harmless treatment environment-friendly device, in the actual working process, after being put into the primary crushing chamber, the large number of crop straws can fall on a cutting blade of a cutting rotating roller for primary cutting crushing treatment, materials after primary treatment fall into the secondary crushing chamber for deep secondary crushing treatment under theaction of gravity, so that the large straws are treated more exquisitely, and favorable conditions are provided for subsequent incineration treatment; and in the treatment process, an electric telescopic rod is adjusted to make an opening and closing side baffle to conduct inlet plugging, not only can be the plugging problem caused by too fast falling of the large bulk materials solved, but alsosplashing broken slag materials in the treatment process can be blocked very well, so that the harm to surrounding people due to the fact that the broken slag materials splash to the exterior of the device is prevented.