本文之目的，在說明並探討通用土壤流失公式中水土保持處理因子的選取。首先說明水土保持處理因子的物理意義與參數值的訂定，接著探討通用土壤流失公式用於非農業開發行為時所遭遇水土保持處理因子選取的困難，最後提出水土保持處理因子選取的建議原則，以提供做為土壤流失量估算時水土保持處理因子參數值選取的參考。

The objective of this paper is to discuss the appropriate value selection for Conservation Practice Factor (P Factor) in Universal Soil Loss Equation (USLE). Physical significance as well as determination process of the P Factor is first discussed, followed by the possible difficulties in value selection. Principles of value selection are suggested at the end so that general guideline can be followed during soil loss estimation.