Following the method of the coefficient K[1] and using the simple analytical wavefuntion of the Weakest Bound Electron Potential Model (WBEPM), we have studied systematically the oscillator strengths and lifetimes of the high Rydberg states (n~40) of atom Li in every case of probable adjustment of node numbers and obtained the adjusting rule for cach transition serie, the results agree with calculated oscillator strength methods by other authors. This shows the effectiveness of the coefficient k method on studying the properties of high Rydberg states of alkali atoms or alkali-like ions.