To apply smaller-scale geothermal generation such as high temperature hot spring field about 90˚C, we carried out a development project of a 50 kW class Kalina cycle geothermal power generation system. From 2010, on site generation project is progressing at Matsunoyama hot spring field in Niigata Prefecture at middle of Japan. This is first test using a 50 kW class Kalina system that potential is estimated as 723 MW using hot spr ing fluid in Japan without drilling. Before starting generation, we analyzed geochemistry of Takanoyu #3 test well, and surrounding wells to estimate the stability of production of hot spring fluid. And we estimated low scaling risk to heat exchanger from equilibrium calculation