Jet spreading width is one of the important characteristics of water jets discharging into the air.Many researchers have dealt with measuring this width,and contact measuring methods on the water jet surface were employed in a lot of the cases.In order to avoid undesirable effects caused by the contact on the jet surface,we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width.In measurements,a transmitter emits sheet-like laser beam to a receiver.The water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow.The minimum and maximum values of the shadow width are measured.In addition,pictures of the water jet are taken with a scale,and the shadow width is measured from the pictures.The experiments on various needle strokes were performed.Three kinds of width consistent with the jet structure were obtained.In the results,it can be concluded that our non-contact measuring methods are feasible.The data of jet spreading widths and jet taper were obtained and are useful for future applications. Jet spreading width is one of the important characteristics of water jets discharging into the air. Many researchers have dealt with measuring this width, and contact measuring methods on the water jet surface were in a lot of the cases.In order to avoid induced effects caused by the contact on the jet surface, we introduce non-contact measuring methods with a laser instrument to the measurements of jet spreading width. In measurements, a transmitter emits sheet-like laser beam to a receiver. water jet between the transmitter and the receiver interrupts the laser beam and makes a shadow. minimum and maximum values ​​of the shadow width are measured. in addition, pictures of the water jet are taken with a scale, and the shadow width is measured from the pictures. experiments on various needle strokes were performed.Three kinds of width consistent with the jet structure were obtained. the results, it can be said that our non-contact measuring methods are feasible.The da ta of jet spreading widths and jet taper were obtained and are useful for future applications.