Distributed acoustic sensing (DAS) technology has been a promising tool in various applications. Currently, the large size and relatively high cost of DAS equipment composed of discrete devices restrict its further popularization to some degree, and the photonic integration technology offers a potential solution. In this paper, we demonstrate an integrated interrogator for DAS on the silicon-on-insulator (SOI) platform. The design of the chip revolves around a Mach–Zehnder modulator (MZM) transmitter and a dual-quadrature and dual-polarization coherent receiver. The integrated interrogator supports multiple DAS schemes, including the time-gated digital optical frequency domain reflectometry (TGD-OFDR), which is adopted for system performance evaluation. 59 pε/$\sqrt{\mathrm{Hz}}$ strain resolution in 12.1 km sensing fiber with 1.14 m spatial resolution (SR) is realized. Besides, along 49.0 km sensing fiber, 81 pε/$\sqrt{\mathrm{Hz}}$ strain resolution with 3.78 m SR is achieved. The results show that the integrated interrogator has comparable performance to the discrete DAS system. To the best of our knowledge, this is the first dedicated on-chip DAS interrogator, which validates the effectiveness of the blend of photonics integration and DAS technology.