Abstract: By theoretical analysis this Hake's paper has pointed out the two shortcomings in the practical application of C. J. Hooke's lubrication status diagram the Greenwood equation which is different from the D. Dowson's equation has been employed and that the two equations' coefficients and exponents are very different. The second is that in Hooke's diagram there isn't any connection with A. N. Grubin's equation. With the two short-comings it is impossible to choose and apply line contact E. H. D. lubrication theory to the practical application. In order to solve this problem, the paper has offered a new E. H. D. lubrication status diagram (Fig. 5-2) that contains five currently well-known line contact E. H. D. lubrication theory. Through analysing the five modern line contact E. H. D. theories the stable boundary curve has been derived. Meanwhile the method of eliminating the calculating error of boundary area oil film thickness has been provided. Finally, the calculating rule of minimum oil film thickness has been carried out and an example is given. Therefore, the theoretical basis for properly choosing Line contact E. H. D. theories (esp. D. Dowson's theory) and the design stage for calculating minimum oil, film thickness are provided.