The bandwidth becomes the major bottleneck of the performance improvement for modern microprocessors. A cache adaptive write allocate policy that improves the bandwidth of microprocessor significantly is proposed by investigating cache store misses. The cache adaptive write allocate policy collects fully modified blocks in miss queue. Fully modified blocks are written to lower level memory based on non-write allocate policy which can switch to write allocate policy adaptively. Compared with other cache store miss policies, the cache adaptive write allocate policy avoids unnecessary memory traffic, reduces cache pollution and decreases load & store queue full rate without increasing hardware overhead. Experiment results indicate that on average 62.6% memory bandwidth in STREAM benchmarks is improved by utilizing the cache adaptive write allocate policy. The performance of SPEC CPU 2000 benchmarks is also improved efficiently. The average IPC speedup is 5.9%.