The work aims to study the effect of zinc on stress corrosion cracking behavior of 316LN in primary hydrochemistry environment of simulated pressurized water reactor and obtain the effect law of zinc on corrosion of 316LN. The crack growth rates of 316LN were obtained by direct current potential drop method (DCPD) in hydrochemistry environment without zinc or with zinc. The effect of zinc on the crack growth rates of 316LN under different stress intensity factors was analyzed. The fracture morphology of 316LN due to stress corrosion and the distribution of elements at the crack tip were observed and analyzed by scanning electron microscopy and transmission electron microscopy. In the aqueous solution without zinc, the crack growth rate was 2.80×10−8 mm/s when the stress intensity factor K was 38.5 MPa.m1/2 and the crack growth rate was 3.51×10−8 mm/s when the stress intensity factor K was 45.5 MPa.m1/2. In addition, in the aqueous solution with zinc, the crack growth rate was 1.29×10−8 mm/s when the stress intensity factor K was 38.5 MPa.m1/2 and the crack growth rate was 1.74×10−8 mm/s when the stress intensity factor K was 45.5 MPa.m1/2. In the aqueous solution with or without zinc, the stress intensity factor promoted the crack growth rate of 316LN, but under the same stress intensity factor, with the addition of zinc, the crack growth rate of 316LN decreased by 46.0%~49.5%, which made 316LN form an oxide film with better protection and higher toughness. Adding zinc to the coolant is beneficial to improving the stress corrosion cracking resistance of 316LN.