Entrainment of surrounding air into premixed acetylene flame leads to a change in velocity and temperature fields. In this paper the mixing process between the premixed acetylene flame and surrounding air, in different regions of the flame, has been analyzed. Conditional and unconditional statistics of the LDA signals were performed using jet and/or air seed. Compared to commonly used unconditional statistics, conditional statistics of velocity fluctuations can give us more data about intensity of turbulent mixing in the flame. Mean velocity, turbulence intensity and probability density function of instantaneous velocities have been measured at different cross-sections of the flame, for premixed acetylene/air mixture with stoichiometric ratio. The velocity field measurements were performed with the laser-Doppler anemometer, while for the temperature field measurements Pt-PtRh10% thermocouple was used. Relations between mean velocities and probability density functions have been established in cases of conditional and unconditional seeding. Mixing factor has been defined as a measure of mixing intensity.