Abstract: To improve in -phase supermode selection for 7 -core fiber laser, a novel cascade system, which consists of a multicore fiber laser as the seeding signal source and a multicore fiber amplifier, was proposed. The transverse supermode competition was analyzed based on a set of rate equations. The ratio of the power of the lower -order modes to the total output power can be reduced to less than 1%, with the optimum distance between the output end of the fiber laser and the input end of fiber amplifier. The results show that the cascade system can improve in -phase supermode selection effectively, which ensures much better beam quality, compared to the multicore fiber lasers with single Talbot cavity.