When phased array radar fulfills tasks such as precise tracking and target identification, and so on, radar resource, such as waveform, data rate, accumulation time, must be changed adaptively. A resource scheduling algorithm based on fixed length scheduling interval is very complicated and does not fully utilize radar resource. An adaptive scheduling algorithm based on variable length scheduling interval is presented. The algorithm performs ordering of radar events based on the importance function of task request, and adaptively adjust the time length of scheduling interval based on the dynamic change of radar resource. The ballistic missile simulator and the multifunctional ground-based phased array radar simulator are modeled using VC language, and distributed simulation is carried out. Through visually observing the implementing process of resource scheduling, and through the two indexes, namely both target tracking amount and rate of time utilization, the scheduling performance is evaluated. The modified algorithm could be implemented easily, and could increase target tracking amount, and save time resource.