In general the measured resistance with a digital multimeter. Users tend to be measured and then displayed on the screen to the user regardless of the value that is accurate or not. The value displayed on screen digital multimeter may be incorrect. As a result from wires access point measurement and other factor that affect to the value of measurement. Thus the study of factors that affect the measurement to get the accurate and more precise and also can be used in the operations. According to international standard quality system requirements for ISO are clearly on the meter or the measuring device must be calibrated and in the certificate specifies the gain calibration and the uncertainty of measurement. Therefore it is necessary to evaluate the uncertainty of measurement to comply with the standard splash. This thesis presents a study of the effect to the measurement resistance in 0.01 ohm to 100 mega-ohm by direct measurement for 2wire & 4wire Loading effect Using different kinds of conductors Thermal EMF and the stability of the resistor. Include the statistical analysis was used to estimate the uncertainty. From this study can be applied to measure the resistance in a variety of accurately and precisely.