The choice of delay time and embedding dimension have no correlation in the process of phase-space reconstruction. Based on this principle, a new idea for determining the embedding dimension is proposed. It uses CAO theory after determining the delay time by the mutual information function. Numerical simulations show that the method is applicable for determining the appropriate delay time and the best embedding dimension. The method can recover the original phase space from the time series effectively, and can be used as an effective method to identify the chaotic signal.