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A small cubic closed vessel with schlieren measurement technique combined with highspeed video camera were used to study limit flame properties under microgravity conditions at atmospheric pressure and room temperature.The rich flammability limit of C3H8/air was determined to be 9.2％ C3H8.Stretched flame propagation speeds,stretched laminar bing velocities and unstretched laminar bing velocities near rich C3H8/air flammability limits were measured at different equivalence ratios.Outwardly propagating spherical flames were used to study the sensitivities of the flame propagation speeds and laminar bing velocities to flame stretch using Markstein lengths.Unstretched laminar bing velocity at rich flammability limit was determined to be 1.09 cm/s.Lewis numbers were less than unity in rich C3H8/air and negative Markstein lengths were concluded.Absolute values of Markstein lengths were found to decrease linearly with equivalence ratios increase.