Dynamic memory allocation mechanism is important aspect of operating system, because an efficient dynamic memory allocator improves the performance of operating systems. In wireless sensor networks, sensor nodes have miniature computing device, small memory space and very limited battery power. Therefore, sensor operating systems should be able to operate efficiently in terms of energy consumption and resource management. And the role of dynamic memory allocator in sensor operating system is more important than one of general operating system. In this pager, we propose new dynamic memory allocation scheme that solves problems of existing dynamic memory allocators. We implement our scheme on Nano-Qplus which is a sensor operating system base on multi-threading. Our experimental results show our scheme performs efficiently in both time and space compared with existing memory allocation mechanism.