The calculation of radial distribution function (RDF) of Kihara rigid core fluids is performed using the sequential-analytic (S-A) method and the effect of reduced rigid core diameter on the shape of RDF is demonstrated. A theoretical equation of state for Kihara fluid is presented and used to calculate its reduced critical properties. It has been shown that the critical compressibility factor of a Kihara fluid is solely determined by its reduced rigid core diameter, and hence the critical compressibility factor of any real fluids can be reproduced through adjusting the value of reduced rigid core diameter. Instead of regression of virial coefficient or viscosity data of dilute gases, it is suggested to determine the parameters of Kihara potential model by matching the critical properties of corresponding substances. It has been shown that the Kihara parameters determined by matching critical properties can be used to predict the properties of both dilute and dense fluids while those determined by fitting dilute gas properties cannot.