The invention provides a method for measuring the bicycle handle bar horizontal pipe external diameter through using a handle bar horizontal pipe external diameter smooth go gauge and no-go gauge cooperatively, the method comprises the following steps: one end of a horizontal pipe is enabled to penetrate a measuring hole of the handle bar horizontal pipe external diameter smooth go gauge, if the end of the handle bar horizontal pipe passes through the measuring hole, the end of the handle bar horizontal pipe is enabled to penetrate into the measuring hole of the handle bar horizontal pipe external diameter smooth no-go gauge, if the end of the handle bar horizontal pipe can not pass through the measuring hole, that the horizontal pipe external diameter meets standard requirements is judged; if one end of the handle bar horizontal pipe can not pass through the measuring hole of the horizontal pipe external diameter smooth go gauge, or can pass through the measuring hole of the handle bar horizontal pipe external diameter smooth no-go gauge, that the bar horizontal pipe external diameter does not meet the standard requirements is judged. The method for measuring the bicycle handle bar horizontal pipe external diameter is achieved through using the handle bar horizontal pipe external diameter smooth go gauge and no-go gauge cooperatively, whether the external diameter of a bicycle handle bar horizontal pipe meets the standard requirements or not can be judged quickly, the results are visual, the use is convenient, and the gauges are durable.