I am working mostly on theoretical observational cosmology, in particular the structure formation of the universe. My main interest is temperature anisotropies of cosmic microwave background radiation (CMB). I am currently working on: reionization of the universe due to early star and galaxy formation, fluctuations of 21cm and evolution of primordial magnetic fields and their observational implications, observational clues about dark energy and dark matter, high energy astrophysics and so on. My research accomplishments include: building a Boltzmann code in the gauge invariant formalism to calculate density and temperature power spectra, proposing a useful fitting formula for the cold dark matter power spectrum,comprehensive study of detailed physical processes on generation of CMB temperature fluctuations (with Wayne Hu),pointing out the possibility of measuring the space curvature of the universe by CMB fluctuations (with Marc Kamionkowski and David Spergel),and developing a realistic galaxy formation scenario based on semi-analytic galaxy formation (with Andrew Benson,Adi Nusser and Cedric Lacey).