The invention provides an offset voltage self-correcting circuit for a comparator. Because offset voltage of the comparator is caused by the semiconductor process parameter randomness, the offset voltage of the comparator also has the randomness; due to the randomness of the offset voltage of the comparator, reference voltage of a parallel comparator in a parallel conversion type analog-digital converter has uncertainty; and, under a condition that the offset voltage of the comparator is serious, the parallel conversion type analog-digital converter even can have a functional error. According to the offset voltage self-correcting circuit for the comparator provided by the invention, the random offset voltage of the comparator can be corrected till the random offset voltage satisfies requirements; therefore, by means of the circuit and the method in the invention, influence of the random offset of the comparator on the function and the performance of the parallel conversion type analog-digital converter can be eliminated; and thus, the speed and the performance of the analog-digital converter, in particular the parallel conversion type analog-digital converter, are greatly improved.