Securities of two special Feistel ciphers with SP-structured round functions against Square attack were studied. By changing the position of P permutation of the round functions in an equivalent manner, some new cryptanalytic results of round-reduced SNAKE(2) and CLEFIA were presented. Time complexity of Square attack against 6-round SNAKE(2) was reduced from 2²⁴ to 2^13.4, and for 6-round CLEFIA, time complexity of Square attack was reduced from 2^34.4to 2^12.4. The results show that, in designing Feistel ciphers with SP-structured round functions, influence of equivalent structures and Square attack should be taken into consideration.