Let λ1,λ2,λ3 be nonzero reals with λ1/λ3 negative irrational. Let φj(u)(1≤j≤3) be smooth functions with derivatives <<u−1(logu)C(u≥3). We prove in this paper that the inequality |∑3j=1λj(pj+φj(p))|<exp(−(log(p1p2p3))1/2) holds for infinitely many triplets of primes pj.