The invention discloses a device for collecting juice of a plant sample. The device comprises a T-shaped structure which mainly comprises a handle and a sampling knife body. The structure is convenient and accurate to operate and is suitable for various operations of holding and sampling, and time and labor are saved; the handle is made of a hard polyvinyl chloride rod, the sampling knife body is made by cutting a stainless steel round rod, and a making material is easy to obtain and durable in use; the knife point is conical, can be effectively pierced into sample tissues and is particularly suitable for juicing a relatively hard plant material; a liquid collection hole is formed in the bottom end of a liquid guide groove to form a collection part of the sample juice, so that a relatively large amount of plant sample juice is conveniently collected. The device is simple in structure, low in cost and easy to manufacture, simple and convenient to operate and high in juicing efficiency, is used for performing large field sampling and juicing, has the work/time/labor saving effects and is suitable for measuring samples of different sizes, and the rapid large field measurement of sugars in the plant samples is facilitated.