Cardiovascular diseases are a major threat to the survival of human beings. An electrocardiogram is used in the diagnosis of heart diseases. But many types of noises are present to deter the quality of ECG signals. Thus, these noises must be filtered using a Digital filter like FIR (Finite Impulse Response) filter. There are different approaches to designing an FIR filter. One of the prominent ways is by using windows. There are other ways of designing the FIR filters but filtering using windows is one of the fastest ways of designing the FIR filters. In this paper different orders to filter has been analyzed and the best order to filter the ECG is found. Using that order different windows of FIR filter has been designed using Xilinx System Generator which is used to filter the noisy ECG signal. Also, various windows have been compared for filtering noises in ECG like Baseline Wander noise and Muscle Artifacts noise. The best window among all the windows is found out using MATLAB Simulink.