An　improved　constant　modulus　algorithm　(CMA)　for　adaptive　multiuser　detection　is　proposed.　According　to　the　two-layered　spreading　modulation　in　the　wide　code　division　multiple　access　(WCDMA)　systems,　the　cyclo-stationary　period　of　multiple　access　interference　is　equal　to　the　least　common　multiple　between　the　lengths　of　the　spreading　code　and　the　scrambling　code.　The　coefficient　update　equation　depends　on　the　cyclo-stationary　period　in　the　improved　algorithm,　instead　of　the　spreading　factor　in　the　conventional　one.　These　appropriate　modifications　make　the　CMA　more　suitable　to　the　WCDMA　systems.　Simulation　results　illustrate　that　the　improved　CMA　can　achieve　1　dB　of　the　gain　on　signal-to-noise　ratio　in　a　4-user　system　on　the　target　BER　of　10-3.