The spetrum for the 6snp Rydberg series of Yb Atom were obtained by using three-step laser excitation. The laser for the first and second step of exoi-tation were oppositely circularly polarized and for the third step was linearly polarized. By the selection rules of the magnetic quantum number m the J value for each spectral line was determined. Some new levels belonging to the 6sns 3Si series (n=26-31) were detected.