Smart antenna and joint detection are the key techniques in the third generation (3G) mobile communication system. But their algorithms are too complicated to meet the requirement of real-time processing. This paper presents a new channel estimate algorithm to solve the problem. With the diversity gain, the principle and technique of simplifying the channel estimate algorithm, structure and decreasing the complexity are discussed in detail. The integrative efficiency of the system combining the array antenna with the joint detection is analyzed. The simulation results show that the algorithm is feasible and effective, and helpful to making the technique of joint detection practical in real system as early as possible.