Imaging flow cytometry based on optical time‐stretch (OTS) imaging combined with a microfluidic chip attracts much attention in the large‐scale single‐cell analysis due to its high throughput, high precision, and label‐free operation. Compressive sensing has been integrated into OTS imaging to relieve the pressure on the sampling and transmission of massive data. However, image decompression brings an extra overhead of computing power to the system, but does not generate additional information. In this work, we propose and demonstrate OTS imaging flow cytometry in the compressed domain. Specifically, we constructed a machine‐learning network to analyze the cells without decompressing the images. The results show that our system enables high‐quality imaging and high‐accurate cell classification with an accuracy of over 99% at a compression ratio of 10%. This work provides a viable solution to the big data problem in OTS imaging flow cytometry, boosting its application in practice.