Abstract: In order to reveal the degeneration mechanism of triple-junction solar cell under intense light radiation, an n-on-1 mode irradiation experiment utilizing a 1 070 nm CW laser as the intense light source was carried out. By summarizing the I-V curves measured after each irradiation, it was found that the short current in triple-junction solar cell will increase when the laser intensity reach to 11.1 W/cm2, other than monotonically decrease with laser intensity increasing in single-junction solar cell. Combined with the relationship between short-circuit current and shunt resistance of current limiting sub-cell and QE of sub-cell, a theory was put up to explain the mechanism of this phenomenon, which indicates that it is the reduction of the shunt resistant in current limiting sub-cell failures its current limiting ability, and finally leads to short circuit current increasing. This theory was verified by equivalent circuit calculation with a simulation program with integrated circuit emphasis.