In single molecule localization based supper resolution microscopy, center position of activated fluorescent maker can be localized by fitting with single point spread function(PSF)or multiple PSFs.The localization error and the total sampling time of the image are dependent on the fluorescence molecule activation density.To obtain the best activation density quantitatively, we simulated the super-resolution imaging process and localized maker positions with single or multiple PSFs.The two algorithms are compared with regard to localization error, recall ratio and number of valid molecules.At last the best activation densities corresponding to different molecules and algorithms are obtained.The results are instructive for the choice of activation density and the control of activation laser intensity.