Abstract: After theoretical analyses,the author considers that the assessment of moistening capacity by a relative permeability method,that is,by the characteristic value of relative permeability curves,the relationship between the permeability ratio of water factes to oil f actes and water-bearing saturability and the ratio of K_w(S_or)/K_o(S_wc)is reliable theoretically.When combined with data from actural oil fields,qualitative results have high reliability.This method used together with a present displacement method and a centrifugal machine method can make moistening Capacity evaluation more objective.When experimental data of moistening capacity is unavailable,factes permeability data can be used to assess moistening capacity in order to make up gaps in the data.