The invention discloses reconfigurable add/drop multiplexer (ROADM) equipment, an optical network system and a transmission method, and relates to the field of optical communication. The ROADM equipment comprises a local uplink and downlink module used for providing an uplink port and a downlink port for transmitting an optical signal; a multifunctional service board card used for processing the received optical signal transmitted by the downlink port, and sending the processed optical signal to client equipment or the uplink port, wherein the processing comprises accessing, electric regeneration and wavelength conversion. According to the ROADM equipment, the optical network system and the transmission method provided by the invention, the multifunctional service board card simultaneouslysupporting the functions of accessing of customer, electric regeneration and wavelength conversion is provided, the simplification of equipment production and engineering configuration is facilitated, the construction cost is reduced, the functions of service accessing, electric regeneration and wavelength conversion can be flexibly configured, staffs only need to go to a site for configuring anoptical module of a client and connecting optical fiber of client equipment when the customer service is accessing, and thus the operating and maintenance cost is reduced.