Productivity evaluation of wells is completed through productivity test of wells. Conventional productivity tests are accomplished at well bottom through measuring production rate and flowing pressure of well bottom in order to determine the productivity index of wells. Productivity index is a parameter to evaluate productivity of wells. However, some wells are difficult to measure their bottom pressure and the productivity index cannot be obtained. In order to evaluate the productivity of wells effectively, productivity evaluation method was improved with measurement at wellhead other than at well bottom. Test of well productivity at wellhead is completed through the determination of nozzle flow equation, which can determine the nozzle productivity index to evaluate the productivity of wells. The nozzle productivity test is completed through measuring flow rate of wells and the size of choke nozzle, which can calculate the nozzle productivity index. The nozzle productivity test can be done simultaneously with the production of wells without any negative effect on the production of oil and gas and any additional cost. Nozzle productivity test is quite simple and practical to the conventional test at well bottom.