Abstract: The cumulative fission yields of shortlived nuclides ⁸⁸Rb, ⁹⁵Y, ¹⁰¹Mo, ¹⁰¹Tc, ¹³⁸Cs^g, and ¹⁴²La in thermal neutron induced fission of ²³⁹Pu have been determined by gamma-ray spectrometry relative method. ⁹⁷Zr is selected as the reference nuclide. The determined cumulative fission yields are given as following: the Y(⁸⁸Rb)=(1.32±0.05) %, Y(⁹⁵Y)=(4.69±0.22）%, Y(¹⁰¹Mo)=(6.13±0.32 )%, Y(¹⁰¹Tc)= (6.10±0.22)%, Y(¹³⁸Cs^g)= (6.24±0.24)%, Y(¹⁴²La)=(4.74±0.17)%. The major work include HPGe detector efficiency calibration, sample sealing and irradiation, gamma-ray measurement and data analysis. The determined nuclides are located in left, middle, right of light group, and in middle, right of heavy group for asymmetric fission model. The accurate yields data supply a gap for domestic nuclear database, and reflect the fission products mass distribution character in thermal neutron induced fission of ²³⁹Pu.