Embodiments of the present invention provide a signal processing method, a network apparatus, and a system. The method includes: mapping a received first client signal into a first ODUflex; mapping the first ODUflex into an optical channel data tributary unit (ODTUCn.X) including X tributary slots, where X is a non-integer; and multiplexing the ODTUCn.X into an optical channel payload unit (OPUCn). According to the signal processing method provided in the embodiments of the present invention, carrying efficiency can be improved when a fine-grained service is transmitted, and complexity is relatively low.