The heavy snowfall in wintertime due to abnormal climate often led to collapse of the plastic greenhouse. A main mechanical reason for the greenhouse collapse is the insufficient moment resistance of a steel pipe used as rafter. As an additional potential reason for collapse, it may be that the strength of connection can affect the global behavior of the greenhouse. It is because the out-of-plane resistance of slender greenhouse frame can become weak when the hookup between pipes is unstable or the strength of connector is below standard strength. In the experimental program, this study evaluates slip load of connector practically used in farmland between rafer (vertical member) and purlin (horizontal member). To investigate the slip load or clamping force of four-types of pipe connectors, the loading tests were carried out with a loading jig designed. As test results, the slip loads or clamping forces of most of the pipe connectors available in the market were not up to standards intimated from Rural Development Administration.