This paper presents a new method to calculate control delay at signalized intersection or other types using speed-time data. For the control delay which composed of deceleration delay, stopped delay, and acceleration delay, it is important to determine the critical points of each delay. This paper uses speed as well as acceleration to determine the critical points and get an accurate result. Different with other researches, it uses the area that composed of real time speed curve and desired speed curve, divided by the downstream speed, to get the control delay precisely. This method needs less data than other methods and can be applied to any traffic condition including variant desired speed or volume. This paper also provides a rapid method, which doesn’t need to determine the critical points, to estimate control delay, and the precision is acceptable.