To protect reservoir during drilling, the drilling-in fluid is generally converted into reservoir protection fluid by adding proper graded temporary plugging materials based on the average radius of pore throat in the reservoir. The main materials include the bridging particles and film-forming agent. In order to achieve the purpose of low damage during drilling, the bridging particles are optimized by the ideal filling theory (IPT) and the film-forming agent is adopted. Based on these results, the synergistic reservoir protect technology is developed and the temporary plugging mechanism is analyzed. Laboratory evaluation and field tests showed that the plugging rate and recovery rate of cores treated by the developed drilling-in fluid are both over 90%, thus, the developed drilling fluid systems have a better reservoir protection effect than conventional systems and can help to increase daily oil production.