With the rapid growth of cloud computing, usability has become a key factor in evaluating cloud products. However, there is a lack of scientific tools to assess usability, making it hard to quantify and analyze data effectively. While prior studies have explored this issue, their evaluation systems are either insufficient or unsuitable for cloud products. This study aims to develop a usability scale specifically for B2B cloud products to measure user experience. Using grounded theory, a theoretical framework was constructed, leading to an initial evaluation system. The Delphi method was then applied to refine the system, resulting in a preliminary scale. Based on classical testing theory, the scale items were analyzed and screened, producing a final scale with three dimensions: task efficiency, information clarity, and system reliability, totaling 10 items. Reliability was tested using Cronbach's α and split-half reliability, while validity was assessed through exploratory (EFA) and confirmatory factor analysis (CFA). The findings show that the scale items have moderate difficulty and strong discrimination. The overall Cronbach's α of 0.9 indicates high reliability, and the CFA results (χ2/df = 1.622) suggest a good model fit and strong structural validity. This study enriches usability research in cloud computing by providing a robust tool for evaluating cloud product usability, ultimately supporting continuous improvement in user experience.