To enhance the security of optical stealth transmission system, an optical stealth scheme based on code shift keying-optical code division multiple access (CSK-OCDMA) technology is proposed, and a 2.5 Gb/s experiment system is setup. The optical source of stealth channel is a low cost distributed feed back (DFB) semiconductor laser, and the public channel is optical transform unit (OTU) near wavelength division multiplexing (WDM) optical networks. The experiment demonstrates that the stealth channel can transmit back to back without bit error, and the penalty for public is only 0.1 dBm. When the stealth channel work without bit error is promised, the difference between public and stealth channels can be 24.6 dBm for the largest. After introducing the forward error correction (FEC), the system can transmit 100 km without bit error.