A spectrophotometric method with an attachment made by ourselves was used to measure the transition temperatures (TJL) from aqueous solution into lyotropic liquid crystalline phase of potassium myristate (KMy). The transition process was shown clearly by an absorbance, A, vs. temperature, T, curve. TIL was obtained from the intersection point of two curves on a plot of δA / δT vs.T¯ TJLmeasured by our method can be compared with reported data. The solubilization of small amounts of inorganic (potassium oxidate) or organic (diphenyl ketone) additive can shift the transition temperature, and TJLrose with increasing concentration of additive. Potassium oxidate or diphenyl ketone in KMy-H2O system made the system form a lamellar liquid crystal instead of the original hexagonal liquid crystal, which was considered to relate to increase of the TJL.