In the environment of multiple tasks which requirements can be satisfied by the capacity of sole key work center, using the algorithm,an optimum processing sequence can be found th.

Although it is more complicated than the key machining center law,it is obvious to optimize the degree and more close to the optimal result.

Based on the concept of critical work in operative planning for network method, a method which can directly find the critical works in vertical graph for op- erative planning for stream-hned process.

Then,a case study shows that the shortage of earned value method depends on ignoring the critical work and quality,and its solution is that the method should integrate critical route and introduce a midst variable called "Earned Quality Value".

The total float time is one of the important time parameters of the work,and its value is the basis to determine the critical works and pathes.

Making use of the flexible scope of the non-key work in a way is the key of carrying on the network diagram excellent turn and the reasonable excellent turn network can bring favourable economic performance.