Abstract: The fact that when computing transition of Landau system due to light, the integration variable of computing matrix element xmk,k, ym,k isn＇t dτ = dxdydp but dτ = dxdy is indicated, and that the matrix element Ym,k should be expressed as ympy,kpy^0, is also indicated, and the transition selection principle of Landau system due to light is revised.

Key words: Landau system, transition due to light, matrix element