The invention provides wide-frequency and low-voltage side trigger control method and device thereof for a series connection thyristor valve unit. The device comprises a current source circuit, a thyristor circuit, an output bus and a magnetic loop transformer, wherein the current source circuit is connected with the thyristor circuit; the thyristor circuit is connected with the output bus; and the output bus is connected with the magnetic loop transformer. The control method comprises the following steps of: providing a current source with flexibly varied output current mode; when the thyristor needs not to be triggered, outputting the direct current with constant output current amplitude value by the current output bus; and when the thyristor needs to be triggered, outputting the alternating current with constant output amplitude value by the current output bus; and triggerring the thyristor by using the secondary side of the magnetic loop on the bus. The invention adopts a no-gap transfer between the direct current with constant amplitude value and the high-frequency alternating square wave current with constant amplitude value, and ensures the front edge of the first trigger pulse and the number of output paths of the trigger pulse can be conveniently adjusted; and the control circuit and a secondary edge circuit of the magnetic loop have simple structure and low cost.