A daily generation scheduling method which can carefully consider the load variation rate is presented. According to the varying tendency of the load curve， a day is subdivided into certain subintervals using the combination method with the characteristic load of every subinterval extracted. As a result， the loads of a few longer subintervals that represent the periods of gentle load variations are closer to the actual situation. By contrast， during abrupt load variation， more subintervals with shorter time duration depict in detail the load behavior in the pick-up and drop-down process and provide sufficient buffer time to get over the critical peak and valley loads. Based on the bottleneck analysis， the full-stage optimal algorithm is used to make the daily generation scheduling. Compared with the traditional one， the method proposed has several advantages， e.g.， better optimization effect without increasing any computational workload， increased economic benefits， smoother active power output of generation units， easier coordination with the automatic generation control（AGC）， and reduced operation burden for dispatchers. An example of IEEE 30-bus system shows the effectiveness of the method.