The invention relates to an all fiber open-cavity FP-type light fluid sensor provided with a side face fluid channel and mainly aims at solving the technical problems of low interference spectrum contrast ratio and low resolution ratio of an existing all fiber open-cavity FP-type light fluid sensor. According to the adopted technical scheme, the all fiber open-cavity FP-type light fluid sensor provided with the side face fluid channel consists of two sections of standard single mode fibers and a hollow-core fiber, wherein the two sections of standard single mode fibers are welded with the leftand right ends of the hollow-core fiber, a cavity of the hollow-core fiber, the right end face of a first standard single mode fiber and the left end face of a second standard single mode fiber forman FP cavity, the side face at the connecting position of the hollow-core fiber and the second standard single mode fiber is processed into a conical face so as to form a microfluid channel. Due to the fact that two reflecting faces of an interference cavity of the sensor are very smooth, the interference spectrum contrast ratio is very high, and the resolution ratio of the sensor is higher. The all fiber open-cavity FP-type light fluid sensor has the advantages of being simple in manufacturing process, low in raw material cost and the like.