At present, the Proof-of-Work (PoW) mechanism of blockchain wastes a lot of computational power and electric power, and the Proof-of-Stake (PoS) mechanism is prone to bifurcation and makes the rich get richer due to the nothing-at-stake and unlimited growth of rights and interests, which cannot guarantee the stability of blockchain. In order to overcome the shortcomings of the two above mechanisms, an improved consensus mechanism of blockchain named Proof of Work and Stake (PoWaS) was proposed based on PoW and PoS. First, the difficulty of hashing calculation was reduced and the maximum value of difficulty was limited to reduce the computational power and electric power resources spent in searching for nonces. Second, the upper limits for the effective coin holding time and the coin age were set to prevent the problem of unlimited wealth of the rich caused by the infinite growth of the coin age. Third, with the concept of credit value adopted, the credit value was assigned to each node, and the credit value was increased or decreased based on node behaviors. Finally, the competition waiting time was added, and the time spent searching for nonces, coin age, and credit value were used to calculate a value named pStake. The node with the largest pStake gained the right to pack and account. A blockchain of PoWaS consensus mechanism with six nodes was built to carry out experiments. Experimental results show that the PoWaS can reduce the waste of computational power, speed up the block mining and balance the competition of accounting rights.