Abstract: In this paper，the author studied the model of finite sum Σ_{i = 1}ⁿ ξ_{i =} of wide upper orthant dependent random variables，investigated the issue of tail probability of finite sum Σ_{i = 1}ⁿ ξ_{i =} by using Markov inequality and a standard truncation method. Under a few of given assumptions，the author obtained a new inequality of tail probability for finite sum Σ_{i = 1}ⁿ ξ_{i =} of the wide upper orthant dependent random variables. The obtained results play an important role in the precise large deviation，the ruin probability，etc. in probability theory.

Key words: wide upper orthant dependence, probability inequality, random variables