Bitwise exclusive OR operation has been widely applied in electronic engineering, automatic engineering, mechatronic engineering, computer science and cryptography. Bound estimate of the operation becomes necessary for algorithm designs of many areas. This article presents bound estimates of both a general form and 3 incremental forms of the operation. The general form can be used in analysis of the operation for general purpose and the 3 forms can be used in incremental analysis of the operation. Theorems with their proofs are presented in detail.