Abstract: An improved AMI code being suitable for telemetry system is proposed. It is realized through inserting redundancy Bit into the binary data stream to be synchronized rapidly and steadily. It has no long continuous zeroes. Its properties are analyzed, such as code efficiency, error Bit rate, power spectrum, the acquisition probability of the first frame marker. This type of code has the similar power spectrum to the original AMI code, and though its code efficiency decreases, rapid synchronization will avoid losing data and increase the credibility of data. In addition, the implementation of this code is described in detail.