Rapid and absolute distance measurement based on dual femtosecond lase rs has been widely carried out recently and the corresponding precision analysis becomes necessary and impo rtant.This paper presents a variety of precision analyses in distance measurement based on dual femtosecond lasers,mainly including quantum noise of the laser,repetition frequency stability,data acquisition and processing.The statistical results of measured distances and time intervals between equivalent sampling sig nals are obtained by experiments.At the same time,the equivalent sampling model based on dual femtose cond lasers is built up for comparison.Firstly,both simulated and measured results show that the typical las er quantum noise has as large as ~10μm influence on measurement precision and it first increases then decreases in one ambiguity range. Secondly,the stability of laser repetition frequency brings an uncertainty of a bout 10－10·L (L is the distance to be measure d),which will increase with the measured distance.Thirdly,data acquisition and processing leads to hundreds of nanometers of uncertainty,and the selection of sampling rate should be balanced between the high accuracy and high processing performance.In addition,both quantization noise and sampling clock in data acquisition have li ttle effect on the ranging precision. Analyses and evaluations of various factors can serve as valuable references for dual femtosecond lasers ranging system and other similar ranging systems.