In order to obtain genetically stable, high-yield, laccase-producing strains, Ceriporiopsis subvermispora was induced by $N^+$ ion implantation and subcultured. The results revealed that, with energy of 30 keV and a dose of $80{ imes}10^{14}$ ions/$cm^2$, a relatively high increase in mutations and positive mutations were achieved. Three screened high-yield strains (NL3, NL4, and NL6) were obtained and subcultured. The results of the comparison showed that, NL4 had stable genetic traits and the highest laccase activity (323 U/L). In the course of fermentation, NL4 entered a vigorous growth period 24 h ahead of the original strain, and produced a large amount of laccase during the stationary phase. Up until the sixth day of fermentation achieved the highest laccase activity of 377 U/L, and a corresponding biomass dry weight of 4.2 mg/mL. The relative laccase activity of the per gram dry cells was 89.76 U, which was 4.79 times that of the original strain. The results indicated that $N^+$ ion implantation was an ideal technique for microbial breeding, which could be applied for the improvement of Ceriporiopsis subvermispora.