As the construction industry has advanced and its system becomes similar to the manufacturing industry, it is important to establish the maintenance system for machines and equipments which are used in construction sites. Since enhancement of mechanization in construction industry seems to be continued, authers has been studied about reliability and maitenability of the construction machines and equipments in order to establish maintenance system. This paper describes the productive maintenance for slipform method which is applied to tower shaped structure. In slipform method, machine failure directly damages the whole system criticaly. In part I, folowings are described. (1) The configuration, mechanism and job system of slipform method are examined. Based on the examination, problems of construction method and conditions of method improvement are shown. (2) Based on FMECA for machines which are used in plipform method, improvement of elements and components are achieved. (3) The improved slipform method is applied to actual construction. Investigation of machine and equipment failures is achievd, and data for verification of machine improvements are obtained which are applied to further improvements. On the basis of the analysis of the data which are obtained from the investigation, a tentative proposal of productive maitenance system for slipform method will be shown and described on part II.