A method for sending a random access preamble sequence in a terminal device for communications system, comprising: sending a random access preamble sequence x u,v ( n ), wherein x u,v ( n )= x u (( n + C v ) mod N ZC ), a sequence x u ( i ) with a root sequence number u and a sequence length N ZC satisfies x u i = e − j πui i + 1 N ZC , 0≤ i ≤ N ZC -1, mod represents a modulo operation, and C v is a cyclic shift that satisfies: C v = { d start ⌊ v n shift RA ⌋ + v mod n shift RA N CS v = 0,1 , L , n group RA n shift RA + n ̅ shift RA − 1 d ̅ ̅ start + v − n shift RA n group RA − n ̅ shift RA N CS v = n shift RA n group RA + n ̅ shift RA , L , n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA − 1 d ̅ ̅ ̅ start + v − n shift RA n group RA − n ̅ shift RA − n ̅ ̅ shift RA N CS v = n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA , L , n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA + n ̅ ̅ ̅ shift RA − 1 , wherein N CS is an integer; and for N ZC + N CS 4 ≤ d u < 2 7 N ZC , n shift RA , d start , n group RA , n ̅ shift RA , n ̅ ̅ shift RA , n ̅ ̅ ̅ shift RA , d ̅ ̅ start , and d ̅ ̅ ̅ start satisfy: n shift RA = ⌊ 4 d u − N ZC N CS ⌋ d start = 4 d u − N ZC + n shift RA ⋅ N CS n group RA = ⌊ d u d start ⌋ n ̅ shift RA = max ⌊ N ZC − 3 d u − n group RA ⋅ d start N CS ⌋ 0 n ̅ ̅ shift RA = ⌊ min d u − n group RA ⋅ d start , 4 d u − N ZC − n ̅ shift RA N CS / N CS ⌋ d ̅ ̅ start = N ZC − 3 d u + n group RA ⋅ d start + n ̅ shift RA N CS n ̅ ̅ ̅ shift RA = ⌊ 1 − min 1 n ̅ shift RA d u − n group RA ⋅ d start + min 1 n ̅ shift RA 4 d u − N ZC − n ̅ shift RA N CS / N CS ⌋ − n ̅ ̅ shift RA d ̅ ̅ ̅ start = N ZC − 2 d u + n group RA ⋅ d start + n ̅ ̅ shift RA N CS ; wherein d u satisfies: d u = { p 0 ≤ p < N ZC / 2 N ZC − p otherwise , and p is defined as a smallest nonnegative integer that satisfies ( p ×u)mod N ZC =1. sending a random access preamble sequence x u,v ( n ), wherein x u,v ( n )= x u (( n + C v ) mod N ZC ), a sequence x u ( i ) with a root sequence number u and a sequence length N ZC satisfies x u i = e − j πui i + 1 N ZC , 0≤ i ≤ N ZC -1, mod represents a modulo operation, and C v is a cyclic shift that satisfies: C v = { d start ⌊ v n shift RA ⌋ + v mod n shift RA N CS v = 0,1 , L , n group RA n shift RA + n ̅ shift RA − 1 d ̅ ̅ start + v − n shift RA n group RA − n ̅ shift RA N CS v = n shift RA n group RA + n ̅ shift RA , L , n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA − 1 d ̅ ̅ ̅ start + v − n shift RA n group RA − n ̅ shift RA − n ̅ ̅ shift RA N CS v = n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA , L , n shift RA n group RA + n ̅ shift RA + n ̅ ̅ shift RA + n ̅ ̅ ̅ shift RA − 1 , wherein N CS is an integer; and for N ZC + N CS 4 ≤ d u < 2 7 N ZC , n shift RA , d start , n group RA , n ̅ shift RA , n ̅ ̅ shift RA , n ̅ ̅ ̅ shift RA , d ̅ ̅ start , and d ̅ ̅ ̅ start satisfy: n shift RA = ⌊ 4 d u − N ZC N CS ⌋ d start = 4 d u − N ZC + n shift RA ⋅ N CS n group RA = ⌊ d u d start ⌋ n ̅ shift RA = max ⌊ N ZC − 3 d u − n group RA ⋅ d start N CS ⌋ 0 n ̅ ̅ shift RA = ⌊ min d u − n group RA ⋅ d start , 4 d u − N ZC − n ̅ shift RA N CS / N CS ⌋ d ̅ ̅ start = N ZC − 3 d u + n group RA ⋅ d start + n ̅ shift RA N CS n ̅ ̅ ̅ shift RA = ⌊ 1 − min 1 n ̅ shift RA d u − n group RA ⋅ d start + min 1 n ̅ shift RA 4 d u − N ZC − n ̅ shift RA N CS / N CS ⌋ − n ̅ ̅ shift RA d ̅ ̅ ̅ start = N ZC − 2 d u + n group RA ⋅ d start + n ̅ ̅ shift RA N CS ; wherein d u satisfies: d u = { p 0 ≤ p < N ZC / 2 N ZC − p otherwise , and p is defined as a smallest nonnegative integer that satisfies ( p ×u)mod N ZC =1. <EOS>