The problem of minimal cost routing （MCR） for PSTN/ISDN based video conference networks is addressed in this paper.Even though MCR can be viewed as a special case of well known SPN（Steiner Problem in Networks）

it is still an NP C hard problem.Heuristics algorithm is expected in order to solve the problem in realtime for most of practical applications.One of such algorithms named NJTU algorithm is proposed

which is a modification of the known SPN heuristics algorithms.The performance of NJTU algorithm is evaluated by 28 randomly chosen sample cases.The difference between the results calculated by NJTU algorithm and the optimal solution is minor.Based on the analysis of the algorithm

a routing table method is proposed as well for the applications which has more limited computation capability and/or needs much shorter response time.