The worldwide increasing energy demand and the alarming situation of the depletion of fossil fuel drive us to focus on deriving energy from renewable sources. The solar thermal power generation (STP) uses different types of solar concentrating technologies and many researches in this area have proven that the parabolic trough concentrator (PTC) technology is suitable for power generation. A PTC is a line-focus concentrator which focuses the solar irradiance to fall on the absorber tube and to transfer to the heat transfer fluid (HTF). The PTC work under the temperature range of 60? to 400 C?. The performance of the PTC can be improved by improving the optical and thermal efficiency. In this paper the recent researches on the thermal performance enhancement by using nano fluid and different absorber tube fluid are studied and presented.