Aiming at the multimedia services in the 3G and 4G CDMA mobile communication system, a soft handover model, in which an overlaid cellular architecture including one macrocell and seven microcells with video service, is given, and link equation of CDMA discrete system in frequency domain is established. Balancing the forward link and reverse link, adjusting the parameters such as the distance and direction between mobile station and base station, the relationship between the soft handover add threshold of marcocell system and the load factor of microcell system is analyzed quantitatively, and their corresponding performances are simulated in both time domain and frequency domain. The results are shown: the variance of distance is more sensitive to the soft handover performance than the variance of direction does.