Taking C8051F362 as the core processor, designs FIR filter by means of window function method to develop portable and low cost ECG monitoring device. On Mattlab simulation platform, designs 30 Hz and 40 Hz low pass filters, and makes the two cascade combination for a 50 Hz notch filter, then applies the heuristic method and zero, pole adjustment method to adjust the filter coefficient of notch filter, and makes the filter to meet the requirements of ECG filtering and adapt to transplantation to C8051F362 single-chip computer. Tests the notch filter with a lot of ECG data in the MIT-BIH database, and the results demonstrate the validity and superiority of this algorithm.