A combustor comprising: at least one combustion unit, the combustion unit comprising: a combustor shell, wherein the combustor shell defines a first rich combustion cavity, a second rich combustion cavity and a lean combustion cavity therein, and the combustor shell is provided with a rich combustion injection port in communication with the first rich combustion cavity and the second rich combustion cavity, a lean combustion injection port in communication with the lean combustion cavity, a first rich combustion flame port in communication with the first rich combustion cavity, a second rich combustion flame port in communication with the second rich combustion cavity and a lean combustion opening in communication with the lean combustion cavity thereon; a rectifying device, disposed in the lean combustion opening and provided with a plurality of lean combustion flame ports in communication with the lean combustion cavity, wherein the first rich combustion flame port and the second rich combustion flame port are located at two sides of the plurality of lean combustion flame ports respectively; a primary air adjusting plate disposed in front of the rich combustion injection port and the lean combustion injection port, so as to adjust an amount of injection air; and a secondary air adjusting plate disposed below the combustion unit, wherein the primary air adjusting plate extends downwardly and defines a pressure balancing chamber between the primary air adjusting plate and the secondary air adjusting plate, wherein a first blind passage and a second blind passage are defined between the rectifying device and two side walls of the lean combustion opening respectively, wherein the first blind passage is located between the first rich combustion flame port and the plurality of lean combustion flame ports, and the second blind passage is located between the second rich combustion flame port and the plurality of lean combustion flame ports, characterized in that there is a height difference between the top surface of an outer side wall of the first blind passage and a top surface of the rectifying device and between the top surface of an outer side wall of the second blind passage and the top surface of the rectifying device. a combustor shell, wherein the combustor shell defines a first rich combustion cavity, a second rich combustion cavity and a lean combustion cavity therein, and the combustor shell is provided with a rich combustion injection port in communication with the first rich combustion cavity and the second rich combustion cavity, a lean combustion injection port in communication with the lean combustion cavity, a first rich combustion flame port in communication with the first rich combustion cavity, a second rich combustion flame port in communication with the second rich combustion cavity and a lean combustion opening in communication with the lean combustion cavity thereon; a rectifying device, disposed in the lean combustion opening and provided with a plurality of lean combustion flame ports in communication with the lean combustion cavity, wherein the first rich combustion flame port and the second rich combustion flame port are located at two sides of the plurality of lean combustion flame ports respectively; a primary air adjusting plate disposed in front of the rich combustion injection port and the lean combustion injection port, so as to adjust an amount of injection air; and a secondary air adjusting plate disposed below the combustion unit, wherein the primary air adjusting plate extends downwardly and defines a pressure balancing chamber between the primary air adjusting plate and the secondary air adjusting plate, wherein a first blind passage and a second blind passage are defined between the rectifying device and two side walls of the lean combustion opening respectively, wherein the first blind passage is located between the first rich combustion flame port and the plurality of lean combustion flame ports, and the second blind passage is located between the second rich combustion flame port and the plurality of lean combustion flame ports, characterized in that there is a height difference between the top surface of an outer side wall of the first blind passage and a top surface of the rectifying device and between the top surface of an outer side wall of the second blind passage and the top surface of the rectifying device.