This paper analyzes the reasons that the mistaken transmittance results are prone to occur in a highly transparent liquid measurement by employing a visible spectrophotometer in traditional methods. On the basis of the analysis results, two kinds of simple ways for measuring the transmittance of highly transparent liquid are proposed.One way is to fit both kinds of transparent faces of a colorimetric ware closely together, in which the film is formed with the pending liquid to be tested. This structure is known as the “liquid film reference cell”. The other way is to fit the pending liquid into a 1 cm length colorimetric ware as the reference cell, and fill the pending liquid into a 2 cm length colorimetric ware as the sample cell. With the two methods, several kinds of common liquids are measured and almost identical results are obtained. Measurements show that the transmittances of measured liquids such as alcohol, water are all in 98%~100% at the visible light range. These ways eliminate the mistaken transmittance results and provide effective methods for the measurement of transparent liquid.