Abstract: Continuous Forest Inventory (CFI) is the main method to get the China's forest area,which is conducted in a systematic sampling manner.In this paper,bias and efficiency of these three plot forest measurement methods will be proved by theoretical analysis.The result shows that:1.CV is unbiased,and it has the highest efficiency;2.PLB is also unbiased,but the efficiency is lower than CV;3.DLB is biased,however the population proportion of forest is almost 0 or 1,the result is nearly unbiased;4.CV method,which is unbiased and has high efficiency,should be chosen for remote sensing large-plot inventory.

Key words: continuous forest inventory, forest area estimation, sampling, unbiased, efficiency