As a core resource in software project scheduling, employees' learning and forgetting characteristic can not be ignored. Based on the existing learning and forgetting models, a model describing the dynamic relationship between the learning/forgetting effect and the employees' skill levels is constructed. Then a multi-objective optimization model for software project scheduling considering above improved learning-forgetting model is given. The multi-objective software project scheduling optimization method based on the improved NSGA-II is introduced to solve this problem by using the new encoding mode and gene-based repair method for the infeasible offsprings. Experimental results under different project scales show that, considering the employees' learning ability is beneficial to improve the performances of the optimal scheduling scheme, whereas the employees' forgetting effect makes the duration and cost of the optimal scheduling scheme worse. Thus it is very necessary to give full consideration to the employees' learning and forgetting effects in the software project scheduling problems.