Nowadays, people have paid more and more attention to air pollution which urging researchers to explore different high-performance gas sensors for air quality monitoring. As a representative of air pollution, volatile organic compounds (VOCs) have been studied a lot. Plenty of work about VOCs gas sensors and how to enhance gas sensing performance has been reported. Constructing a heterojunction structure in gas sensor material was considered to be one of the effective methods to improve the performance of gas sensors. In this work, a series of nickel-indium layered double hydroxides (NiIn-LDHs) precursors with different Ni/In atonic molar ratios were synthesized successfully via chemical precipitation methods. And a series of NiO-In2O3 P-N heterojunctioned materials were fabricated by calcining these NiIn-LDHs precursors in the air at high-temperature. Following with an annealing step at H2 atmosphere at different temperatures, these heterojunctioned materials can be used as gas sensing materials to detect low concentration toluene gas. The influence of Ni/In atomic molar ratios and annealing temperatures on gas sensing performance were studied. The results showed that when Ni/In atomic molar ratio was 3.0 and annealing temperature was 500℃, the obtained material showed the highest response to 0.005‰ toluene. In addition, the material also showed high selectivity to other interfering gases (such as 0.005‰ ammonia, acetone, triethylamine, sulfur dioxide, and high-humidity water vapor), and it had shown good stability in a 12-day-testing. A series of characterizations such as XPS, UPS, etc. confirmed that the material Ni/NiO-In2O3 which formed after annealing at 500℃ owns Schottky barrier and abundant oxygen vacancies. The synergistic effect of P-N junction, Schottky barrier and abundant oxygen vacancies lead to the best sensing performance. This work can provide ideas for the development of high-performance toluene gas sensors.