The invention provides a method for estimating performance of a partial treatment casing. Firstly, a partial treatment casing gas compressor is divided into a treatment casing gas sub-compressor and a solid-wall casing gas sub-compressor in the circumferential direction; then, a treatment casing performance estimation model assumption is given; and finally, on the basis of characteristic parameters of the two gas sub-compressors, parameters of the partial treatment casing are worked out, and a stalling point is judged. Two different experiments of 98% of the rotating speed of a 180-degree treatment area of a transonic high-speed table and a 240-degree treatment area of a subsonic low-speed table are estimated, and results show that under the condition that two characteristic lines of a solid-wall casing and a peripheral treatment casing are known, partial treatment casing characteristics in the treatment area of any angle can be well estimated through a model and can be well matched with experiment results. The characteristics of the partial treatment casing gas compressor are estimated, so that time cost is reduced, and computing resources and experimental resources are saved.