Software process is a human-centered system, with special characteristics in dynamic and continuous evolvement. The physical execution of a defined process will normally deviate from its process model. This paper uses E-CSPE (extended constraints on succeeding and proceeding events) constraints to carry out process validation and deviation measurement. The event constraints are defined based on the process model. The execution of a process instance is recorded down as an event sequence. The event sequence is analyzed to determine how much each event constraint defined is covered or violated. The result can be used to compute the EPD (event constraint based process difference metric) and EAD (event constraint based activity deviation metric) metrics. The EPD metric can reflect the difference between the process execution and its process model, while the EAD metric can provide some evidence for process evolvement.