The Chemical Injection System is designed to inject and control the amount of chemicals or fluids into the tubing to control corrosion in wells, treat paraffin, salt and/or hydrate formation. This can optimize flow assurance, reduce expensive intervention costs, and ultimately optimize production. The system includes Chemical Injection Mandrel (CIM) and Chemical Injection Valve (CIV). The chemicals or fluids are injected through a control line from surface. The check valve in CIV provides absolute protection for the check valves during installation in the well and provides a barrier between the production tubing and the annulus.