借助計算機對混沌序列進行數值分析必須考慮計算機的存儲字長有限這個條件。針對Logistic映射，研究了計算機字長對其混沌特性的影響，由于計算機的字長效應，混沌序列經過短暫的過渡態后演化為周期序列，使用小數據量法計算了處于過渡態和周期態的有限字長混沌序列的最大Lyapunov指數。通過數值計算結果表明：有限字長混沌序列的周期態和過渡態都具有正的最大Lyapunov指數，且小數據量法對有限字長效應是魯棒的。最后，給出了一個加長有限字長混沌序列演化周期和過渡期的耦合方法。To analyse the chaotic time sequences by computer should consider the finite word length of the computer. As to the logistic map, this paper studies the effect of finite word length to its chaotic characters. Due to the finite word length of computer, the chaotic sequences will turn into periodic ones after short interim. The maximum Lyapunov exponents are calculated by the small data sets method. The results show that both periodic and transitional chaotic sequences have positive maximum Lyapunov exponent, and the small data sets method is robust to the finite word length of the computer. In the end, a coupled method to improve the period and interim length of chaotic sequences is given.