The invention aims to solve fixing and leveling problems of a small prism in a measuring process, particularly in a process of meeting an inclined steel structure. The invention provides an automatically-balanced small prism fixing and adsorbing platform. The automatically-balanced small prism fixing and adsorbing platform comprises a sleeve with a hollow inner cavity and a base with a hollow inner cavity. The upper end of the sleeve is opened and the lower end of the sleeve is sealed. The sleeve is internally provided with a separation plate. The separation plate is used for dividing the inner cavity of the sleeve into upper and lower cavities. The lower cavity of the sleeve is internally filled with heavy objects. The small prism is inserted into the upper cavity of the sleeve. An annular groove is formed in the outer wall of the sleeve. The base is made of a permanent magnet. The upper end of the base is provided with an opening. The edge of the opening is a flange. After the lower end of the sleeve is inserted into the opening, the flange is embedded into the annular groove.