Injection device capable of filtering in two directions

The injection device comprises a needle cylinder and a filter membrane device, the upper end and the lower end of the filter membrane device are respectively provided with a connecting port, the filter membrane device is matched with the needle cylinder through the connecting ports, and the outer wall of the needle cylinder is sleeved with an auxiliary pipe. According to the utility model, the auxiliary tube is sleeved on the outer wall of the needle cylinder, so that the first baffle plate at the bottom end of the main tube is attached to the second baffle plate at the bottom end of the needle cylinder, and meanwhile, one side of the baffle plate is propped against the top end of the membrane filter, and a user presses the first baffle plate with fingers, so that the baffle plate has a certain limiting capability on the membrane filter; therefore, when a user extrudes and pushes the piston push rod of the filter needle cylinder to filter liquid to be detected in the filter needle cylinder, the filter membran