The purpose of this paper is to analyze the planning of the Nereid monument. Through the analysis of the dimensional proportion of the building, the following conclusions were given. In the planning of this building the proportional relationships between the dimensions are simple. The planning started from the decision of the internal dimensions of the naos as 9 feet by 11 feet (1 foot = 0.310m). Many dimensions are defined by the successive system of proportion. Many of the plannig dimensions in the Nereid monument are complete figures, suggesting that the construction aspect was taken into account at the planning stage.