CDMA based third generation mobile communication adopts Rake receiver to get diversity gain for multipath signals. This paper first analyzes why traditional CDMA delay tracker fails when multipaths are closely spaced (1-2 chips apart). Then we propose a novel adaptive coherent CDMA tracking loop. This new structure uses an adaptive delay detector which is able to suppress the disturbance from neighboring multipath components. Experiments show our method can track multipath profiles with 1-2 chips apart. The proposed structure is also low in complexity. It's well suited for the downlink tracking in WCDMA/CDMA2000 standard.