Diamond anvil cell (DAC) is a kind of high-pressure generator that is frequently used in the laboratory and plays an important role in the field of high-pressure research. When pressure-transmitting medium (PTM) in DAC can just provide non-hydrostatic pressure, it will be difficult to accurately measure the pressure of the sample by using the ruby fluorescence method. The same cases frequently emerge under ultra-high pressure conditions. If there is a material with dual functions of transmitting pressure and measuring pressure, the pressure values of the sample under non-hydrostatic conditions might be measured accurately according to the principle that the closer the positions are, the more similar the pressures are. Apparently, it is important to search for the material with dual functions of transmitting and measuring pressure. In this paper, a ruby particle and a small drop of ionic liquid [C₄mim][BF₄]were loaded into a DAC, a series of high-pressure environments were provided by compressing the [C₄mim][BF₄]. Simultaneously, the fluorescence spectrum of ruby and the Raman spectrum of [C₄mim][BF₄] was obtained under high pressures. By analyzing the positions of the R₁ line of ruby, the pressure values of [C₄mim][BF₄] were obtained. By analyzing the widths of the R₁ line of ruby, it was found that the hydrostaticand quasi-hydrostatic pressures provided by [C₄mim][BF₄] were in the ranges of 0~6.26 and 6.26~21.43 GPa, respectively. It could be speculated that [C₄mim][BF₄] can use as PTM in the pressure range of 0~21.43 GPa. In addition, [C₄mim][BF₄] is a liquid phase Ⅰ, liquid phase Ⅱ, amorphous phase I, and amorphous phase II in the ranges of 0~2.28, 2.28~6.26, 6.26~14.39, and 14.39~21.43 GPa, respectively. By analyzing the positions of ν_(B-F) and ν_(ring) as the characteristic Raman peaks from [C₄mim][BF₄], it was found that they followed linear changes with increasing pressure during the above four phases of [C₄mim][BF₄]. What's more, the formulas of pressure and position of ν_(B-F) and ν_(ring) were given. The formulas are very important for [C₄mim][BF₄] to be a pressure gauge. To sum up, [C₄mim][BF₄] has the dual functions of transmitting pressure and measuring pressure and can use simultaneously as the PTM and the pressure gauge. The research results provided an important basis for accurate measurement of sample pressure in non-hydrostatic environments and provide a new solution to the inaccurate measurement of sample pressure under ultra-high pressure conditions.