Abstract: Lightlike helices in 3D Minkowski space are studied. First, the Frenet frame of lightlike curves in 3D Minkowski space is given and the method of describing lightlike curves with lightlike curvature functions is proposed. Then, the lightlike helix definitions are given, which are classified as general lightlike helix, first slant lightlike helix and second slant lightlike helix according to that the inner product is a constant between the tangent vector, principal normal vector, binormal vector of a lightlike curve and a fixed direction vector, respectively. Finally, the characterizations of lightlike curvature functions of lightlike helices are studied and their specific expression forms in different conditions are obtained.