Abstract　 　　 

    Galaxy galaxy lensing is now considered to be a direct detection of the dark matter surrounding the luminous galaxies. However, it suffers systematics as PSF, CCD noise e.t.c, which makes lensing a difficult task. In this talk, I would like to introduce the galaxy-galaxy lensing in theory and methods to correct the systematics . Finally, the lensing signal from LSS, especially from filaments.