Abstract: A number of Poa pratensis buds with heat tolerance were selected after a heat stress treatment of 49℃ while at the multiple bud clumps stage in vitro. When the buds had developed into seedlings, they were transferred into pots to grow under natural conditions. After about half a year, several of these lines and the donor variety were treated by heat stress, and changes of chlorophyll fluorescence (Fv/Fm photochemical efficiency of PSII), MDA content, rate of ion leakage, and the chlorophyll content were measured. The stressed lines had less damage than the donor variety showing that we obtained P. pratensis with improved heat tolerance, and created a new heat tolerant germplasm of P. pratensis.