In this paper, the design and development of wideband microwave pyramidal absorbers for semi anechoic chambers has been presented. This work is carried out with the goal of simulating and fabricating the microwave absorber using conventional and newest material such as polyurethane to save the budget cost with security and reliability. The simulation of absorber is performed via Computer Simulation Technology (CST) for the microwave frequencies 1 GHz to 20 GHz. The outcomes of simulation proved good absorbing efficiency and better RCS reduction compared to traditional microwave absorber. The reflection level is less than -30 to -10 dB over the desired frequency range of 1 GHz ~ 20 GHz.