The production of unconventional fields such as tight oil or gas and shale oil or gas has increased significantly from the year of 2011 to 2021 in China. Unconventional resources such as shale oil or gas and tight oil or gas have attracted more attention in the recovery of upstream fields and become important replacement areas towards conventional fields. The hydraulic volume fracturing technology in horizontal well mainly features with multi stages and clusters, high displacement, high sand and liquid ratio, and replacing ceramic particles with quartz sand, which imposes higher technical requirements on downhole tools, temporary plugging and diverting materials. The existing temporary plugging materials mainly include chemical temporary plugging agents and balls. As a high-strength and adaptive temporary plugging material, knots have been deployed to various pads of unconventional fields over the last decade. It was found by field applications that the above-mentioned materials exhibit drawbacks such as high density, poor stability and lower engaging rate. To address the issues, Research Institute of Petroleum Exploration and Development (RIPED), PetroChina proposed a novel dissolvable composite temporary plugging tool. The inner structure of the tool is a low-density hollow dissolvable sphere, which is tightly covered with one dissolvable rubber layer. By adjusting dimensions of the hollow dissolvable sphere, the total density of the tool can be changed between 1.05 and 1.15 g/cm3. During the workbench test, the dissolvable composite temporary plugging tool was completely dissolved within 10 h at 90 ℃ and 1% potassium chloride solution. The prototype with O.D. of 25 mm can withstand external pressure of 110 MPa and was specified as differential-pressure-resistance of over 70 MPa in the seat-engaging test. Dissolvable composite temporary plugging balls have been successfully applied in shale-oil fields in Ordos Basin. On a certain pad locating in Changqing Oilfield, temporary plugging and diverting operations were successfully conducted in 14 stages and 96 clusters of one single well. A total of 268 temporary plugging balls were pumped down and the maximum pressure rise upon temporary plugging was measured as 17.9 MPa. It was proven by the field trial that the newly-developed dissolvable composite temporary plugging tool meets the requirement of strict hydraulic fracturing and temporary plugging operations towards unconventional fields.