Guideway straightness is one of the most basic geometric error of ultraprecise machining tools and measurement devices, and it has influence on the machine tool. The research status of measurement methods for guideway straightness was analyzed, the disadvantages of different measurement methods in straightness measurement of ultraprecise guideway were pointed out, and a new method for straightness measurement was proposed. The short standard flat ruler was used for being joined which was machined and saved easily, and least squares method was used to deal with measurement data in order to acquire all straightness measurement data of guideway with large distance. The test indicates that the guideway measurement shape and data of the joining method are consistent with those of long standard flat ruler. Therefore, the meter level guideway straightness measurement and error compensation control can be realized by this method to improve the machine tool precision.