In this paper, a wireless portable electrocardiogram (ECG) monitoring system that suits for continuous cardiac activity recording is proposed. An analog front end (AFE) integrated circuit is the solution for biopotential recording. The microcontrollers are embedded with the program in order to control the wireless data transmission, and store data in the flash memory. To display and analyze the result, C# base software has been developed to communicate with the device via Bluetooth interface. A modified real time QRS detection algorithm with auto threshold method is implemented for calculating the heart rate in real time and offline application. The performance of developed prototype is evaluated in amplitude and heart rate accuracy with standard calibration equipment. To evaluate the QRS detection algorithm, standard 24-hr MIT/BIH normal sinus rhythm database are applied to compare with the result. The algorithm sensitivity and +P is 99.85% and 97.74%, respectively. This proposed system will be foundation for uncomplicated wireless portable ECG monitoring system in the future.