The invention discloses a kit and a detection method for determining the copper ion concentration in a water environment. The kit comprises a B1 solution, a color comparison tube, a glass graduated pipette, a copper standard color scale solution, and a copper standard color scale or copper standard color comparison card. The kit is advantage in simple preparation method, low cost, good B1 solution stability, high extraction rate, low detection time, no requirement on other experimental equipment and professional and technical personnel, easy implementation, convenient carrying, and suitability for on-site detection of visual colorimetry. Main reagents in the kit are provided in forms of working fluids, and are packaged independently. The reagents are easy to preserve, and are suitable for on-site applications. According to the detection method, a reaction is fast. Under room temperature, only 7-10 minutes are needed from sample treatment to detection result acquiring. All organic phases of the method are not soluble in water, such that waste liquids can be separated and recovered after detection, and can be processed and reused. Therefore, no secondary pollution is caused, and requirements of modern detection technologies are satisfied.