In this paper, we propose a low complexity quantum principal component analysis (qPCA) algorithm. Similar to the state-of-the-art qPCA, it achieves dimension reduction by extracting principal components of the data matrix, rather than all components of the data matrix, to quantum registers, so that the samples of measurement required can be reduced considerably. Both our qPCA and Lin's qPCA are based on the quantum singular value thresholding (QSVT). The key of Lin's qPCA is to combine QSVT and modified QSVT (MQSVT) to obtain the superposition of the principle components. The key of our algorithm, however, is to modify QSVT by replacing the rotation controlled operation of QSVT with the controllednot operation, to obtain the superposition of the principal components. As a result, this small trick makes the circuit much simpler. Particularly, the proposed qPCA requires 3 phase estimations, while the the state-of-the-art qPCA requires 5. Since the runtime of qPCA mainly comes from phase estimations, the proposed qPCA achieves a runtime of roughly 3 5 of that of the state-of-the-art. We simulate the proposed qPCA on the IBM quantum computing platform, and the simulation result verifies that the proposed qPCA yields the expected quantum state.