Lee, T.-Y. JACoW Geneva, Switzerland 978-3-95450-180-9 10.18429/JACoW-NAPAC2016-THPOA61 English 1226-1227 THPOA61 ion lattice emittance quadrupole electron Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-NAPAC2016-THPOA61 https://jacow.org/napac2016/papers/thpoa61.pdf As the upgrade of PLS, PLSII is a 3 GeV light source in 12 super-periods (281.8 m circumference) with 5.8 nm design emittance and can store electron beam up to 400 mA with 3 superconducting RF cavities. PLSII lattice is a double bend achromatic (DBA) lattice with 2 straight sections for each cell (24 straight sections). After comple-tion of PLSII, multi-bend achromatic lattice has widely been adopted to accomplish low emittance. This paper discusses how a minimal change can modify the PLSII's DBA to a quadruple bend achromatic (QBA) lattice and reduce the emittance to about a half value.