The two major classes of topological semimetals,Weyl semimetals and nodal line semimetals,are characterized by linear band-touching at zero-dimensional points and one-dimensional lines,respectively.We show that a circularly polarized light drives nodal line semimetals into Weyl semimetals.The Floquet Weyl points thus obtained are tunable by the incident light,which enables investigations of them in a highly controllable manner.The transition from nodal line semimetals to Weyl semimetals is accompanied by the emergence of a large and tunable anomalous Hall conductivity.Our predictions are experimentally testable by pump-probe ARPES or transport measurement in thin film samples.