For calibration of displacement measuring sensors, a portable calibration system using a homodyne laser interferometer was developed. The system is directly traceable to the Meter definition. And it is also transportable due to use of a laser source coupled by an optical fiber, so it can be used for calibrating the sensors attached to the length measuring instruments. In general, the accuracy of the laser interferometer with short measuring range is mainly limited by nonlinearity error. In order to reduce nonlinearity error, offsets, amplitudes and phase of the sine and cosine signals from interferometer are manually adjusted and compensated by ellipse fit. Nonlinearity error is reduced to ±0.15 ㎚ by software-based compensation. On calibrating sensors, the system can be used in a static or a dynamic way. When the system is used statically with measuring time of 2 minutes, the expanded uncertainty at 95% confidence level is estimated as (1.2 + 2.6 × 10?? L) ㎚, where L is moving distance in ㎚.