In order to effectively produce deep，low-permeability and sensitive heavy oil reservoirs which is extremely difficult to develop，this paper takes Block Wang152 of Wangjiagang Oilfield in Shengli Oil Province as an example to conduct in-depth analysis of development difficulties and flow mechanism，and on this basis，puts forward an innovative technology of viscosity reduction induced flooding. Besides，in virtue of the single-tube sand-filling flooding model experiments，reservoir engineering methods and numerical simulation methods，the paper studies the development technology limits of deep，low-permeability and sensitive heavy oil reservoirs. According to the proposed technology，viscosity reduction is implemented in producing wells for them to enhance huff-and-puff recovery；early continuous flooding with variable concentrations and later viscosity reduction and flooding with variable concentrations and slugs are implemented in injection wells. The results show that the technology helps increase the recovery of deep，low-permeability and sensitive heavy oil reservoirs by 14.3%. The key parameters of the development technology such as the flooding mode，the effective cycle，the concentration of viscosity reducers，and the injection volume are also optimized and determined. The pilot test results of Wang152-X6 well group in Block Wang152 show that，by September 2020，the peak daily oil production of the well group was 11.5 t/d，which was 5.4 times higher than that before the test. After 157 days of flooding with a cumulative injection of 6 534 m3，the viscosity reduction induced flooding proved effective in all production wells，and the cumulative oil production of the well group reached 856 t. Due to the significantly improved development，the oil recovery was predicted to increase by 11.0%，which has realized the transition from un-producing to effective producing of deep，low-permeability and sensitive heavy oil reservoirs.