A simple fast correlation attack is used to analysis the security of Bluetooth combiner in this paper. This attack solves the tradeoff between the length of the keystream and the computing complexity needed to recover the secret key. We give the computing complexities of the attack algorithm according to different lengths of the known keystream. The result is less time-consuming than before. It is also shown that the secu-rity of the modified Bluetooth combiner by Hermelin and Nyberg is not significantly enhanced. A simple fast correlation attack is used to analyze the security of Bluetooth combiner in this paper. This attack solves the tradeoff between the length of the keystream and the computing complexity needed to recover the secret key. We give the computing complexities of the attack algorithm according The result is less time-consuming than before. It is also shown in the secu-rity of the modified Bluetooth combiner by Hermelin and Nyberg is not significantly enhanced.