Provided is an ST2 antigen binding protein, such as a mouse, human, chimeric or humanized antibody or antigen binding fragment thereof that specifically binds to ST2. Also provided are nucleic acid molecules encoding the above-mentioned antibodies and antigen binding fragments thereof, and an expression vector and host cell for expressing the antibodies or antigen binding fragments thereof. Further provided are methods for preparing and using the antibodies and antigen binding fragments thereof. The methods comprise treating and preventing IL33/ST2-mediated related diseases or conditions.