In this paper a sequence estimator of CDMA communication system is suggested. A sequence estimator uses Galois Field operation. A sequence estimator can provide another CDMA pilot signal which is un-modulated spreaded signal. A estimated sequence signal and received signal have no correlation. Tow signals can be summed using MRC(maximal ratio combine) method. The stronger signal can be added as a larger ratio, but the weaker signal can be added as a smaller ratio. We can distinguish strong signal using SNR estimator. Therefore it is possible to receive an additional pilot signal, and to support more reliable communications by using sequence estimator.