Based on research advances, practical experiences and the chacters of southwest China mountain agricultural region, this paper analyzed the difficulties and their causes in cultivated land productivity assessment, discussed the deficiencies in the current assessments, and put forward some further sustainable research issues. Firstly the whole study region should be divided into several sub-zones according to the disparities in climates and terrains, and then estbliahsed the corresponding assessment indexes and their weights. For the regions interlaced with paddy fields and drylands, especially for southwest China, paddy fields and drylands should be assessed separately due to the obvious differences in their productivities and factor weights. Furthermore, the choice should be stressed for the interpolating methods for each assessment unit, it could be done on the bases of generally correct understanding about the collected data. Besides, all links in the assessment process should be noticed, for they could immediately and remarkably influence the assessment results and agricultural production and pattern reconstruction.