It is necessary to get the dimension of re-constructed phase space before calculating the chaotic statistical. characteristics. Six methods are offered which are the measurement of the on unaltered maximal characteristic value, the measurement of changeless geometry mete, the measurement of false nearest neighbors, the measurement of minimum prediction error, the measurement of minimal Shannon entropy, and the measurement of the experience evaluation. An engineering case is given to explain the application of the measurements of the unaltered maximal characteristic value and minimal Shannon entropy.