Abstract: The micrometers for external measurements with reading accuracy of 0.01 mm have also considerably wide applications in the fields of the dimensional control and precision measurements for mechanical engineering, but the elevation of its measuring accuracies is limited by some fundamental construction defects. In this paper the author has given the principal analyses and descriptions on the subject about the different kind of errors of the micrometers.Further in this article, there are also researches, analyses and comparisons to the different standards dealing with micrometer from some countries, to which the author has brought out his own opinion from the practical point of view. Besides, some improvements and notable features about the testing methods for micrometer are discussed too.