Abstract: Known Bits(KB) method is a way of increasing the performance of turbo code by inserting known bits periodically in a code word without increasing in complexity. KB method normally causes uneven protection due to the process of random interleaving. This problem can be solved with a KB interleaver to ensure uniform distribution of KB. It is found that KB interleaver can improve the performance of turbo code with pseudo random interleaver or S-random interleavers. This method also makes a rate-matching to be easy which is fairly important for systems using turbo codes.