StepFun

What it is StepFun (阶跃星辰) is an AI company based in Shanghai. Its legal name is Shanghai Jieyue Xingchen Intelligent Technology Co., Ltd. It was founded on 6 April 2023 by three former Microsoft employees: Jiang Daxin, Zhu Yibo and Jiao Binxing ^[1]. Jiang Daxin (姜大昕) is the chief executive. Zhu Yibo leads the systems work, and Jiao Binxing, a former head of Bing's core search team, leads data ^[2].

The company focuses on multimodal models, which handle text, images, video and audio rather than text alone ^[1]. Investors have counted it among China's six so-called "AI Tiger" start-ups ^[1].

Origins The name comes from the step function, a mathematical function that changes value abruptly at a given point. Jiang registered the company about a month after being promoted to Microsoft vice president in March 2023 ^[3].

The company made its public debut on 23 March 2024 at the Global Developers Pioneer Conference in Shanghai. It announced the Step-1 language model, the Step-1V multimodal model and a preview of the trillion-parameter Step-2 model. It also launched two consumer apps, Yuewen (跃问) and Maopaoya (冒泡鸭) ^[1].

Main features StepFun's models are organised as a series. Step-1 and Step-1V were announced first, followed in July 2024 by the official Step-2 model, Step-1.5V and the Step-1X image generator, released at the World Artificial Intelligence Conference (WAIC, 世界人工智能大会) ^[4].

In 2025 the company open-sourced several models. Step-Video-T2V and Step-Audio were released in February with the carmaker Geely. Step1X-Edit followed in April, and the 321-billion-parameter Step 3 in July ^[1]. It also formed a model-chip alliance with Huawei (华为), Biren (壁仞科技), Moore Threads (摩尔线程) and Enflame (燧原科技) to optimise its models for domestic chips ^[1].

Its models reached a large installed base through phone makers. By the end of 2025 they ran on more than 42 million devices, through partnerships with about 60% of China's major phone brands. Its voice models and its AgentOS system were also used in Geely cars ^[5].

In 2026 the company released Step 3.5 Flash in February, Step 3.7 Flash in May and Step 5 Preview in September ^[1][8].

Place in the field StepFun is one of the companies that raised large sums to compete in China's model race. In January 2026 it raised a Series B+ round of more than 5 billion yuan (about US$719 million). Investors called this a record for China's AI model sector. Yin Qi, the founder of Megvii (旷视科技), became chairman, while Jiang Daxin remained chief executive ^[5].

On 25 February 2026 Bloomberg reported that StepFun was planning a Hong Kong initial public offering (IPO) ^[1][7]. In May 2026 the company completed a round of about US$2.5 billion. Investors included Huaqin Technology (华勤技术), OmniVision (豪威集团), ZTE (中兴通讯) and the Hong Kong Investment Corporation (香港投资基金公司). Earlier, in late April, StepFun had converted into a joint-stock company and dismantled its red-chip structure. At that point it had more than 500 staff ^[6].