A method of applying the extended Hückel molecular orbital method for the evaluation of crystal field parameters in the rare earth compounds is presented. The charge distribution in the crystal field and the effect of the outer coordinated sphere on the calculation of the crystal field parameters is discussed. From the calculated charge distribution, the crystal field parameters A 20〈 r 2〉, A 40〈 r 4〉, A 60〈 r 6〉, and A 66〈 r 6〉 of praseodymium ethyl sulfate crystal and praseodymium trichloride crystal have been obtained. The calculated results are in agreement with the experimental data. Some possible sources of the error in the calculation are discussed.