A converter station valve tower thyristor positioning system and a work method thereof relate to the high voltage conversion field; the rapidity and accuracy of an existing thyristor positioning system need to be improved; the converter station valve tower thyristor positioning system comprises a thyristor position arrangement rule analysis module, an alarm storage module, an alarm position plaintext transition module and a display module; the alarm position plaintext transition module can translate the position code information formed in a thyristor alarm event into a position plaintext according to the thyristor arrangement rules obtained by the thyristor position arrangement rule analysis module. The system and method can convert a backstage non-plaintext alarm message into the real thyristor position plaintext, and can use a graphical language to mark the fault thyristor positions, thus greatly reducing the time of operation personnel searching for thyristors in a valve hall field,improving the thyristor position positioning accuracy up to 100%, and earning precious time for implementing accident coping in the field.