在定义三参数区间数的基础上，给出了三参数区间数的运算关系；然后将权重为区间数的多指标决 策问题转化为指标取值为三参数区间数的多指标决策问题；在三参数区间数理想方案点定义的基础上，给出了 权重为三参数区间数的逼近理想点法；最后将其应用于某城市公交线网的优化调整中。结果表明，该法科学合理、切实可行。

To evaluate the cost risk and the schedule risk of the spaceflight project,  the schedule-cost (S-C) correlation coefficient is directly appointed according to the experts' experience usually.  This paper deduces SDMCU (the schedule distribution model considering the effect of the cost uncertainty),  and then proposes the approximate formula to estimate the ln (S)-C correlation coefficient based on the models of SDMCU and CDMSU (the cost distribution model considering the effect of the schedule uncertainty).  Furthermore,  an approximate relationship expression of the S-C and the ln (S)-C correlation coefficients is put forward according to general facts and the Taylor expansion,  and advanced by means of mass numerical validation is the general rule of obtaining the estimation value of the schedule-cost correlation coefficient based on the historical data.