This paper introduce a kind of latex synthesized by the method of soap-free emulsion polymerization. The latex without adding stabilizers can be used for oil well cement. The monomers are styrene (St), methyl methacrylate (MMA) and butyl acrylate (n-BA), and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) is used as polymeric emulsifier. The code of the soap-free latex is JAS. By using some analytical tools, such as Zeta Potential Measurement Analyzer, Transmission Electron Microscopy, Thermogravimetric Analysis and so on, the relationship between the amount of AMPS and JAS latex’s emulsion particle size distribution, particle Zeta potential, the thermostablity is investigated. The JAS latex without adding stabilizers can be used for oil well cement, and the latex cement is made. After cured for 72 h, the JAS latex cement’s Compressing strength and Cementing strength are higher than the base slurry cement’s, improving 13.35 MPa and 1.15 MPa respectively. This indicates that the JAS latex can significantly improve the performance of oil well cement.