Abstract: A method for estimating a cardiovascular characteristic parameter comprises steps of: obtaining a first action amount of a subject and a sensing signal of a cardiovascular aspect within a first time interval, wherein the first action amount is located within a first action amount threshold range; determining, based on the first action amount threshold range, a first estimation scope for estimating the cardiovascular characteristic parameter; and determining an estimation value of the cardiovascular characteristic parameter based on the above steps. The present disclosure estimates a cardiovascular characteristic parameter mainly based on a sensing signal, an action amount, an action amount threshold range, and a corresponding estimation scope. The action amount and the corresponding estimation scope reduces a certain computation capacity of corresponding exemplary apparatus, such as PPG sensor or ECG sensor, smart wristband, or smart watch.