From the theory of SHG of Gaussian-like beams. We come to the conclusion th.it the power of the second-harmonic wave is approximately proportional to the square of the fundmentalwave power for frequency doubling of Gaussian-like beams with high conversion efficiences. Based on this, a new intracavity frequency doubling scheme of mixing-mode beam, i.e. quasi-CW pumping, is proposed. By using such scheme, the output power can be increased by a factor of 2, a fact that has been proven by theory and experiment. From thermal conduction equation, it has been found that the beam propagation parameter through a YAG rod under quasi-CW pumping is 22% lower· than that under CW pumping. If other factors are taken into account, the decrease will become 30%. By experimental njessureiiierite, we found that the thormal focal lengtli is increased and the divergence angle is decreased，as predicted by theory.