The invention discloses a formwork system suitable for a large-diameter manual hole digging annular foundation pile and a construction method. The formwork system comprises a reference column, connecting pieces, steel pins, steel formwork horizontal supports, a manual hole digging pile guard arm, a steel formwork fixing rod, an annular steel formwork, a steel formwork longitudinal connecting hole,a steel formwork horizontal connecting hole, steel formwork horizontal support length adjusting devices, annular foundation pile concrete, an annular foundation pile formwork system, a reference column connector, an annular foundation pile top and an annular foundation pile bottom. The formwork system has the beneficial effects that good support can be provided for the annular steel formwork, sothat the overall stability of the formwork system can be effectively improved, the problem that the annular steel formwork is not easy to install and disassemble is effectively solved while the tightconnection of the annular steel formwork is guaranteed, no connecting device is arranged between the annular foundation pile formwork system and the manual hole digging pile guard arm for connection,it is ensured that a foundation pile reinforcement cage can be integrally hoisted, and the construction progress is accelerated.