Plant-soil feedback (PSF) is a structuring force of plant community. Theoretical studies have highlighted either litter or microbial mediated PSF. However, the difference between seedlings and adults in litter feedback and vulnerability to above- and below-ground enemies has been ignored, effects of foliar defense trait on PSF strength have also been overlooked. Models also did not examine possible outcomes of the two main experiment designs (sterilization and inoculum approach), which have been proved may show different results. We present a size-structured PSF model coupling litter and microbial feedback to identify PSF strength for plants with different trait along the tolerance-resistance continuum, and to detect the difference between the two experimental approaches. We show that tolerant plants perform best in pathogen-free soils, while resistant plants grow better in the presence of pathogens. We also show that inoculum approach should be preferred because it reflects plant trait and pathogen impact on nutrient cycling, while simply excluding pathogen by sterilization approach fail to detect this difference. Our model can serve as a framework for further studies integrating herbivory induced litter quality changes and pathogen saprophytic growth.