Thanks for the answer, but if the manufacturing order isn't start yet why openerp can't cancel it ? Or forced us to cancel manufacturing order before like it does with Delivery Orders ?

I am wondering about this as well for v15. I can imagine customization that would do this.

Something like (pseudo code):

@api.model
def write(self, vals):
res = super(ProductTemplate, self).write(vals)

if 'some_canceled_state_field' in values and values['some_canceled_state_field']:
# find mo's and cancel them with their cancel method.
mfg_order = self.env["the.mfg.order.model.name"].search([("origin", "ilike", order_name)])
for order in mfg_orders:
#cancel them
order.cancel()
return res

Surely someone has written one up that could share it here.