This work investigates the start-up characteristics of linear compressors in a refrigeration system through experiment and simulation.Experiments are carried out by a refrigeration test system with a linear compressor controlled by a LabVIEW platform.A simulation model that considers the nonlinear process of gas force is set up on the basis of Runge-Kutta method for linear compressors.Compared with the experimental results,the simulation errors are within 15％,including the unstable state.The influences of ambient temperature and power frequency on linear compressors are studied through experiments.Unstable phenomena exist at 25℃ ambient temperature compared with the designed ambient temperature of 35℃.The unsteadiness mechanism is analyzed by simulation.Simulation analysis indicated that two sensitive stages of linear compressors,namely,starting to pump and touching top dead center,are unstable.Furthermore,properly increasing equivalent mass (approximately 3％) or spring stiffness doring the design stage can be a practical method to improve the stability of linear compressors.