The present invention discloses a linear motor traction system cogging force reduction method. The traction system comprises four three-phase primary permanent magnet linear motors, the cogging forces of the linear motors are subjected to Fourier decomposition to obtain the harmonic number m with maximum amplitude; a space distance between a first primary permanent magnet linear motor and a second primary permanent magnet linear motor is (k1+1/2(2*m)) [Tau]s, and the whole thereof is a first combination body; a space distance between a third primary permanent magnet linear motor and a fourth primary permanent magnet linear motor is (k2+1/2(2*m)) [Tau]s, and the whole itself is a second combination body; the cogging force of the first combination body is subjected to Fourier decomposition to obtain the harmonic number n with maximum amplitude; and a space distance between two combination bodies is (k3+1/2(2*m)) [Tau]s, wherein k1, k2 and k3 are positive integers, and the [Tau]s is a stator polar distance. The linear motor traction system cogging force reduction method can substantially weaken the cogging force, can improve the thrust fluctuation performance and keep the static state average thrust of a single motor invariant so as to maintain the original passenger-carrying capability of a train.