Zhongji Innolight Co., a Chinese optical transceiver manufacturer and supplier to Nvidia, rose to become the largest stock on the CSI 300 Index on June 4, 2026, holding about a 5.3% weighting in the index [1]. The company surpassed Contemporary Amperex Technology Co. Ltd. (CATL), which has a 4% weighting, to claim the top position [1, 2].
This index weighting reflects the market capitalization of free-float shares from the 300 most valuable companies listed on the Shanghai and Shenzhen stock exchanges [2]. Zhongji Innolight’s shares nearly doubled in 2026, continuing a fivefold gain from 2025, reflecting strong investor interest in the stock [2].
The company’s rapid growth is fueled by robust demand for its high-speed optical modules used in artificial intelligence data centers operated by major hyperscalers. Key customers include Alphabet (Google), Amazon, Meta Platforms, Huawei, and Alibaba [2]. Alphabet accounted for 22% of Zhongji Innolight’s sales, followed by Amazon with 11%, Meta Platforms with 6.4%, Huawei with 5%, and Alibaba with 1.9% [2].
The increase in weighting on the CSI 300 was confirmed by data on June 5, 2026, showing Zhongji Innolight at about 5%, ranking first among constituents [2]. This advance places it ahead of other leading stocks such as Kweichow Moutai, which currently holds a 3% weighting in the index [1].
Zhongji Innolight’s rise reflects its critical role in supplying optical transceivers needed for expanding AI infrastructure globally. The company’s stock performance and growing market position demonstrate investor confidence in its technology and customer base.
The CSI 300 Index will update weightings regularly as company valuations shift. Zhongji Innolight’s position will be closely watched in upcoming revisions to the index.
